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More cuttings produced during gas drilling due to higher mechanical penetration rate and the cuttings usually tend to be larger in the bottom and smaller uniform in size when back to the wellhead. It is indicating that cuttings should appear successive breaking within the process of migration. According to particle collision broken theories, the successive breaking phenomenon was analyzed, and the calculating method of crash velocity for the occurrence of secondary breaking was given in this paper. Meanwhile, the breaking process matrix and the particle size distribution function were applied to study the re-cracking process of cuttings migration in the whole wellbore. The calculating results show that the cuttings in the wellbore were broken first in the form of the uneven size volumetric fracturing and then progressively turned into the surface fracture of the uniform process, and ultimately was tending towards stable particle size distribution state. [ABSTRACT FROM AUTHOR]

It is easy for Coiled Tubing (CT) to deform a plastic elongation because of many factors, such as the residual stress etc, in the process of coiled tubing service. The paper analyses the cause of coiled tubing plastic elongation and explains the principle of the same elongation. Coiled tubing plastic elongation has four mainly reasons: axial load causes plastic elongation, thermal causes plastic elongation, pressure difference causes plastic elongation, helical buckling causes elongation. The theoretical calculation formula and calculation method for CT plastic elongation are summarized. Calculation examples about CT plastic elongation give some basic CT plastic elongation conclusions by comparative analysis of relation curve on calculated value. The CT plastic elongation is more complicated and more obvious than conventional tube. The elongation caused by axial load and the shortening caused by helical buckling are larger than others and should be focused on the need to consider in the progress of coiled tubing service. The thermal expansion and the elongation caused by pressure difference are smaller than above all and should be given due consideration in the progress of coiled tubing service. Total elongation deformation is made up of four parts: the plastic elongation caused by axial load, thermal expansion, plastic elongation caused by pressure difference and the shortening caused by helical buckling. The four elongations may cancel partially each other, so the total elongation deformation generally is smaller than every single elongation. [ABSTRACT FROM AUTHOR]

The conventional weighting admixture of ultra-high density water-based drilling fluid may lead to viscosity effects, which means that the drilling fluid could lose its flow property due to high viscosity. In this paper the properties of barite optimized by using surface activation and particle classification. First the optimum dosage of surfactant (RAB) was determined after experiments of electric potential effect and rhelogy behavior; furthermore, on the basis of classical accumulation theory and plenty of laboratory experiments, the particle size ranges under different modulus and the optimum particle classification were calculated by using the distribution equation of Dinger-Funk. An industrial specific barite was produced by adjusting and optimizing production process and then was applied into several deep wells with ultra-high pressure in Sichuan area. Finally, the ultra-high density water based drilling fluid (with the density of greater than or equal to 2.65 g/cm³) is successfully prepared on site. The applied results show that the ultra-high density water-based drilling fluid with special barite has characteristics of weighted high density, easy controlled rhelogy behavior, and anti-salt & water invasion resistant. It can satisfy the actual requirement of practical drilling operation, and thus worth popularizing. [ABSTRACT FROM AUTHOR]

A steady state coupling model combining seepage flow and pipe flow was established for herringbone horizontal well, which will provide fundamental theory reference for completion design of complex structure wells. This model focused on open hole completion system and was solved by infinitesimal section method. Each part of pressure drop in coupling flow with existence of completion screen pipes was discussed in detail, and then the flowing pressure and flow rate distribution profiles were given. The analysis results show that, formation sand stack layers in annular space between screen pipes and wellbore produce an additional pressure drop, which make a negative influence on the seepage flow. The flowing pressure and flow rate distribution profiles of wells with screen pipe are lower than those of open hole under the same flowing pressure, and the affection degree primarily depends on sieve size of screen pipe as well as formation sand grain distribution, and partly controlled by local seepage interference. The size of screen pipe, parameters of eyeholes in base pipe and mass transfer in pipe wall have an effect on well bore flow, which makes wellbore flowing pressure distribution profile of overall production section is steeper than that of open hole under the same proration production. By comparing the calculated results with the classical model solutions, the model proposed in this paper is proved reasonable. [ABSTRACT FROM AUTHOR]

Well productivity prediction is the key point and important reference to oilfield development and artificial lift design. In order to establish a method and model of productivity prediction for the CO2 flooding well, considering the influence of formation pressure and drainable radius, permeability and relative permeability curves, crude oil components, CO2 concentration and skin factor over well productivity, this paper have designed the orthogonal test and a number of reservoir numerical simulation calculations. Then based on the method of Vogel to establish well productivity equation of dissolved gas-drive reservoir, the first model of well productivity prediction for CO2 flooding was established through translating the numerical simulation results into integrated dimensionless. Example applications have launched in 2 pilot wells in Jilin oilfield and the results showed that the average relative error of 11 data points is 4.27% while the maximal relative error is 9.07%. This indicated that the prediction precision of this method and model proposed in the paper is relatively high. So it has certain application value in preparing oilfield development plan and well lifting design of CO2 flooding. [ABSTRACT FROM AUTHOR]

Inflow Control Devices(ICD) represents a new well completion technology for controlling bottom water which provides uniformity of the inflow profile by restricting high specific inflow segments while increasing inflow from low productivity segments. This paper studys with numerical simulation the effects of the proportion of high permeability zone, permeability grading, the length of control section and the flow rate of control section on the water breakthrough performace of a reservoir with bottom water using ICD,and determines the optimum placement of inflow control device, the flow resistance rating and the length of control section. The results show that the smaller the proportion of high permeability zone is and the larger permeability grading is, the better the water breakthrough performace of a reservoir with bottom water is in heterogeneous reservoirs, and ICD mounting location, length and limit flow rate have an importantment of water breakthrough performace of a reservoir with bottom water. In order to make the water control and oil increment effect maximization, ICD should be installed in horizontal well section of high permeable zone, and the length must be equal to or slightly higher than the high permeable zone length. The flow rate in the high specific inflow segments shold be as close as possible to the average flow rate in all sections. [ABSTRACT FROM AUTHOR]

Considering the practical production figures and block mechanism analysis of Well WAA-1, the coiled tubing acid washing measure for removing pollution is proposed, and then the operation background, project design, operation process as well as effect evaluation of coiled tubing acid washing treatment are illustrated in this paper. By adopting the way of tripping the coiled tubing and controlling the lift speed and injecting rate, the acidizing fluid can be distributed equally in the horizontal interval. While wash head impulse vibrate, it will produce pressure agitation to screen pipe to wash deeply and remove damage. [ABSTRACT FROM AUTHOR]

With the rapid development of native microbial enhanced oil recovery technique in China recent decade, paraffin removal and prevention by microbial and huff & puff with single well have became mature explore technologies in oil fields and have been wide scale used in many oilfields taking as production maintain and stimulation measures, respectively. However, the existence of mechanism misunderstanding and technique optimizing still need further study to enhance the effect of treatment and efficiency. Meanwhile, the microbial flooding technology is still on pilot stage, although more than 20 field trials have been carried out. There is no consensus of opinion in microbial flooding and the orientation of technological development is still obscure so that there are difficulties on technology extension. Studies, field tests and applications in recent decade about microbial technology were discussed in this paper, and the several key points in microbial flooding were discussed in detail. On the basis of analyzing on-site experiment patterns and developing trend, some problems that need to pay attention in next research and development in the future have been proposed. [ABSTRACT FROM AUTHOR]

The stick-slip phenomenon is very common in downhole drilling process. It is harmful for drilling project and could damage downhole devices, and even brings about dowmhole accident, which is a threat for downhole safety. So it is significant to timely find and remove stick-slip for drilling operation. Domestic drilling contractors and surface logging companies have attempted to study and predict stick-slip phenomenon at downhole by monitor the driver motor current and rotary table torque. The paper provides a new method to describe the downhole stick-slip phenomenon by measuring actual rotational speed of the lower BHA from MWD magnetic sensor, which give a better insight to the downhole drillstring movement, and classifies the severity of stick-slip to several ranks. The information is send to the surface by MWD so that the driller can take some useful manners to decrease the stick-slip and keep drilling process in safety. [ABSTRACT FROM AUTHOR]

The balance relationship between bottom hole annulus pressure and formation pressure is a key factor to affect the drilling operation safety. Because of the complex and various situation underground, there is a big error between the actual bottomhole pressure and calculated one. The paper introduced a PWD system which can measure the parameters of weight on bit (WOB), torque, annulus pressure, annulus temperature, pressure inside the drill string, etc., and transmit the measurement data to the ground in real time. With the real time measurement data, the wellbore hydraulic model can be corrected in real time, and the underground situation can be interpreted in real time, what is more, the drilling accident can be predicted in real time. The field test proves the accuracy and reliability of the measurement system. Compared with the storage PWD system, this measurement system is more accurate, and has the function of transmitting the measured data in real time, so it can offer powerful technical support for drilling operation. [ABSTRACT FROM AUTHOR]

To further study the mechanism of hydraulic sand blasting perforation and examine the channel pattern and porous depth formed by hydraulic sand blasting perforation, a research on channel pattern of hydraulic sand blasting perforation has been carried out to observe the influence of lithology, displacement and blasting time on hydraulic sand blasting perforation and master the characteristics of fracture initiation. This paper has completed the design and manufacture of both outcrop core and cements targets, and optimized the experimental parameters and integrated tools, which were used to finish the hydraulic sand blasting perforation experiment and the fracture initiation experiment. In order to obtain more real and intuitive channel shape, the specific integrated tool has dissected and drawn the targets. These two experiments show that channels depth caused by hydraulic blasting is shallower than that induced by former laboratory experiment results. Two main channel forms resulting from hydraulic sand blasting perforation are fusiform-channel in the normal perforation target and built-up channel combing fusiform-channel with sword-channel. The two channel induced by hydraulic perforation almost symmetrical in shape. When the fracture is initiated, the depth will increase multiply. these conclusions are very reliable and helpful to further understand the mechanism of hydraulic sand blasting fracturing and improve and widespread this technology. [ABSTRACT FROM AUTHOR]

Aiming at low lift pumping efficiency and high energy consumption of pumping wells in Daqing peripheral low permeability low-yielding oilfield, taking time as one parameter into account during the production parameters optimization of pumping wells, the conventional oil well working system with three parameters "pump diameter, stroke, pumping speed" adjust and transform into four parameters "pump diameter, stroke, pumping speed, time". Taking minimizing energy consumption as the goal and maintaining yield as basis condition, a four-parameter working system optimizing model was established in this paper, and then corresponding calculation software was designed, which could easily and accurately calculated the single well intermittent oil production and reasonable system of work. [ABSTRACT FROM AUTHOR]

The current level of horizontal wells fracturing is simply with single well, and the impact of water injection and well patterns are often neglected in enhancing the capacity of single fractured horizontal wells, which appears serious limitations in fracturing effect. Aiming at enhancing the whole block of the recovery, taking the whole reservoir as study object, this paper established an overall fracturing theoretical model for horizontal wells. Fully considering combined distribution of horizontal and vertical wells, a variety of well patterns containing horizontal and vertical wells were designed, and an optimizing design software for horizontal well fracturing was developed. Based on optimizing the well pattern of horizontal wells overall fracturing, considering different length of horizontal sections, the parameters including numbers of fractures, fracture length, conductivity, crack spacing, crack asymmetric distribution and so on were designed, and then the optimal crack parameters have been obtained to forecast the production performance of fractured horizontal wells (daily production, cumulative production, rate of water content, recovery percent of reserves and so on). The method and software would provide certain reference on enhancing the horizontal wells overall fracturing effects. [ABSTRACT FROM AUTHOR]

Pulse well test is one of interference well tests and conventional methods used to explain parameters can be summarized as tangent method, secant method, plate fitting and parameter matching method. The above methods are all using some special points selected in the production data to match the standard plates when explain the parameters. These methods are characterized by low utilization rate of data, slow explaining rate and poor fitting accuracy. Aiming at these disadvantages, pulse well test wellbore storage and skin factor model was established in this paper, combined with nonlinear regression techniques, an optimal analysis method using bounded trust region was proposed to solve 6 parameters in pulse well test model which include energy storage coefficient, flow coefficient, skin factor, wellbore storage coefficient. Pulse well test production data of one reservoir was fit with this method, and the maximum relative error of fitted values is 6.49% and the average error is only 2.98%. Meanwhile, the method belongs to automatic fitting technique, not affect by human factors, and has super- linear fitting speed. [ABSTRACT FROM AUTHOR]

A suit of heat and pressure preservation sampling system was designed in this paper, which is suitable for high sulfur gas wells in 6500m depth. It is made up of downhole sampling device (DSD) and ground transfer device (GTD), and can collect natural gas in high sulfur natural gas wells and long-time heat and pressure maintaining storage and transportation. So the using of this system can preserve real physicochemical properties of samples and enhance the effectiveness of PVT experiments. A clock controller was adopted in DSD to control automatic collection and record the state parameters in whole course and the vacuum heat preservation interlayer structure and heat insulation coating technique were used to ensure heat and pressure preservation function. Meanwhile, for convenient transferring, the structure of DSD is divided into two demountable parts: electric control chamber and gas sampling chamber. GTD is in a seal cylinder structure equipped with electric control system which possesses gas collection chambers maintaining heat and pressure storage and transportation for long time and H2S leaking emergency treatment abilities. In conclusion, the equipment is featured by compact structure and complete function. It can provide a suit of safe and reliable equipment for sampling in deep and high sulfur gas wells. [ABSTRACT FROM AUTHOR]

Bullet compound perforation technology settled the problems existed in present compound perforation such as low utilization of bombing gun and gas, poor gas fracturing preference followed by perforation. Deviating from the other compound perforating technologies with high energy gas fracturing, bullet compound perforation realize near-well fracturing with blast wave caused by blasting bullet explosion in perforating channels. Technological mechanism, characteristics and index of bullet compound perforation technique were illustrated in this paper. The experiment show that the bullet compound perforation technology is valuable to enhance the productivity of oil & gas wells, and worth application and popularization. [ABSTRACT FROM AUTHOR]

Generally speaking, the horizontal section length of Dual horizontal SAGD wells is longer than that of conventional thermal recovery wells. During the production process of SAGD section, it is prone to steam channeling between production horizontal wells and injection horizontal wells and reserves non-uniform used in the horizontal section, which affect the development performance of SAGD well groups and increase the controlling difficulty. In order to improve the uniformity of producing degree in horizontal section, a uniform steam injection theoretical model was established and corresponding pipes were design in this paper. Trial test in the Feng City SAGD has obtained remarkable results, which is useful to future SAGD expand application. [ABSTRACT FROM AUTHOR]

The ranges of permeability among low permeability, extra-low permeability and ultra-low permeability reservoirs are redefined, and the tight oil reservoir and low permeability reservoir are distinguished. The tight oil formation forming mechanism and development features are discussed, and the difference between Bakken tight oil reservoir and the common low permeability reservoir is pointed out. Also, the paper presents the key technologies and new knowledge of developing tight oil reservoirs in the Bakken play. The new technology and theory of developing Bakken tight oil reservoirs can provide low permeability reservoir development in China with a certain referential value. [ABSTRACT FROM AUTHOR]

Precision screen completion has good sand control capacity, and is suited for horizontal wells with severe sand production. The flow near the wellbore with precision screen is different from that of ideal well in which it includes the radial flow in the distal formation, the convergent flow in slotted liner of the protective layer, the radial flow in intermediate filter layer, and the convergent flow in the hole of the base-pipe. In this paper, the skin factor model of horizontal well completed with precision screen was built up in consideration of formation damage, and an actual computation was performed with this model. The result shows a little difference between the calculated result and actual data, proving the fitness of the model. Through analyzing the sensitivity of the factors, it was found out that the skin factor was largely affected by parameters of damaged formation, the permeability of the intermediate filter layer, the penetration ratio of slits in the protective layer, the slits around the protective layer, the hole density of the base pipe, and phase angle and borehole radius. [ABSTRACT FROM AUTHOR]

Artificial fracture parameter optimization with dimensionless proppant index method is an analytical approach widely used, but the effect of long-term artificial fracture conductivity performance change with time on the well productivity have not been taken into account. The optimization results by dimensionless proppant index method are not the best one in the view of practical production of stimulation wells. In this paper, combined with the experimental results of long-term proppant conductivity, transferring the fracture width and permeability in dimensionless proppant index method into the functions of time, the dimensionless cumulative productivity index has been presented though the integral of dimensionless proppant index with respect to time. And this result will serve as the optimal fracture parameter. Because of variable time being introduced into the formula and considering the change of proppant conductivity performance with time, the calculating method is more suitable in practice and more reasonable comparing to dimensionless proppant index method. The numerical solutions show that greater fracture width and higher concentration of proppant should be reached for low and extra-low permeability reservoirs with long-term conductivity taken into account in order to get more cumulative production. The views of lower demand artificial fracture conductivity and longer fracture for low and extra-low permeability reservoirs should be changed. This method can prolong the validity period of post-treatment production increase for single well and is of significance to evaluate operation effect. It is suggested that the influence of proppant concentration on long-term conductivity should be developed pertinently for certain areas, which could provides reliable reference for the application of dimensionless cumulative production index method. [ABSTRACT FROM AUTHOR]

Since the associative polymer has different solution viscosity forming mechanism with that of HPAM. In this paper, in order to analyze the viscosity loss caused by mechanical shear during associative polymer oil-displacement agent injection allocation process, the effects of mechanical shear on associative polymer solution are studied by combining dynamical laser scattering method, pyrene fluorescence probe spectrometry and atomic force microscopy (AFM). Studies show that the apparent viscosity, viscosityaverage molecular weight and hydrated particle dimension of associative polymer solution decease obviously at the very start of mechanical shearing action. With the increasing of shearing action, numbers of association particles during micro area in the solution is decreasing, but appears slightly recovery after the solution was placed 24 hours, never restores to the previous state. The number of micro-association-area is reduced with the increase of shearing time. Through AFM, the network structures are observed both in the associative polymer solution before and after shearing action and also observed that the hydrated particle dimension and the connections between the particles degrade after shearing. It can be concluded that both the associative polymer molecular chains and association structures damage in the course of shearing action, and because of difficulty of recovery, solution viscosity is fall. [ABSTRACT FROM AUTHOR]

Acid-cleaning technology of screen completion horizontal well is an effective measurement for cleaning the drilling fluid pollution in bore hole, and the acid-cleaning effect directly affects the well productivity. The early stage of acid-cleaning strings in Shengli oilfield has some deficiencies such as incompletely sealed well-washing valve, poor sealing effect of well washing packer and no drainage channels. Such problems directly caused poor acid-cleaning effect on horizontal wells. The acid-cleaning strings were specific modified and the sealing structure of washing valve was improved in this paper. And then well-cleaning packer equipped with flow path was developed. The new technology improves acid-cleaning performance and effectively enhances well productivity of screen completion horizontal wells. [ABSTRACT FROM AUTHOR]

This paper investigated the relationship between coal rock permeability and heating temperature in less than 200 °C through laboratory experiments. And by means of X-ray diffraction analysis and Scanning Electron Microscope, the influence of heat on coal rock permeability was analyzed from perspective of coal chemistry and coal geology. The results shows that coal rock permeability could be significantly increased from less than 0.5 mD to 15 mD by heat treating. Analyzing results indicate that mechanisms may be explained as follows: Firstly, dehydration of coal rock and partly volatile components releasing of coal rock will form new pores. Secondly, desorption of methane molecules and dehydration of gelatinous micro-component in the matrix lead to the shrinkage of coal matrix. Thirdly, coal rock generates hydrocarbon gases after oxidizing reaction of carbon and Hydrogen atoms, and the gas releasing forms tiny cracks and reduces the degree of coal rock compaction. Fourth, coal rock encounters inhomogeneous deformation under thermal stress, and produces uneven small cracks. Finally, the paper proposes a new mode of coal bed methane (CBM) exploitation to enhance CBM recovery by injecting thermal CO2. Above researches may be of great help to the exploitation of CBM reservoirs with low permeability in China. [ABSTRACT FROM AUTHOR]

During the service of casing in acidic gas field, the acidic environment and other corrosion condition can cause casing corrosion. The thinning of casing wall and the appearing corrosion cavity in the internal wall of casing can both reduce the effective strength of casing. Thereby they can affect the collapsing strength and internal pressure strength of casing. It is maily discussed in the paper that the affection on casing strength from stress concentration caused by corrosion cavity. The corrosion cavity of casing is regarded as sphere-like cavity. The mathematical model is established that can calculate the stress concentration factor caused by corrosion cavity, based on the knowledge of plasto-elasticity. The mathematical model is also established, which can calculate the residual intensity of casing after corrosion. The parameters of corrosion cavity affecting the strength of casing are analyzed. It is also analyzed that the relationship between the residual intensity of casing and the depth and diameter of corrosion cavity. [ABSTRACT FROM AUTHOR]

Micro Flux Control (MFC) drilling technology has advantages of detecting early small overflow and leakage and controlling the bottom hole pressure precisely. The core component in this technology is ground automatic throttle manifold, whose agility and accuracy is directly related to whether pressure control can be achieved and its accuracy. This technology has been widely used by several foreign companies, who do not sell relevant equipment and tools, but only provide technical service with extremely high price. To break the monopoly of foreign technology and to reduce drilling cost as well as to develop MFC drilling technology with independent intellectual property right, a set of ground automatic throttle manifold was designed by comprehensively considering the relationship between well bore pressure distributions and throttling flow capacity and based on fluid dynamics and automatic control theory, The field test confirmed that this set of equipment has an excellent function of automatic throttle control. The MFC of well bore can be achieved in 30 s and the pressure error is less than 0.1 MPa. Design and successful field application of this throttle manifold paved the way for the promoting of MFC drilling technology in China and equipment localization. [ABSTRACT FROM AUTHOR]

System efficiency is an important parameter for evaluating the energy consumption of pumping well system. In order to evaluate the gap between the limiting system efficiency of oil well and current level, to explore the potential system efficiency and to improve pumping well system efficiency, this paper puts forward the application mode that combines potential evaluation of system efficiency and simulation optimization design technology based on parameter sensitivity to pick out potential wells and develop optimized well design scheme before putting it into field application through comprehensive consideration about the produced fluid property, fluid supply capacity, system equipment and parameter combination. This technology has been applied in 2,616 wells in Huabei oil field, where the optimization object is identified by analyzing system efficiency potential of wells and the optimization direction is determined on basis of parameter sensitivity analysis, achieving ideal measure effect proved by field application of optimization design. [ABSTRACT FROM AUTHOR]

Considering the strong heterogeneity of carbonate reservoirs, it is very difficult to reach the reservoir at the lower part by conventional acid fracturing due to restrictions of drilling technology and geological conditions if the borehole is relatively far away from the reservoir. This paper, based on the mechanism of artificial interlayer controlling fracture propagation path, puts forward an idea where floating type of diverting agent forms high artificial barrier layer before forcing longitudinal downward propagation of acid fracture. A special floating type of diverting agent TBA of ultra-low density and high temperature and high pressure resistance is developed, which has a density of 0.37 g/cm3, pressure-bearing capacity of 140 MPa and keeps stable at 260 ?. The floating type of diverting agent TBA is studied with respect to the floating law, and digital modeling is used to optimize the time of floating and dosage of TBA to obtain the control parameters of acid fracturing that effectively forces the fracture to propagate downward as far as possible until reaching the reservoir. This acid fracturing technology has been tested in 4 wells in carbonate reservoirs in Tarim basin with excellent effect. [ABSTRACT FROM AUTHOR]

The hydraulic fracturing treatment in oil well is a process of solid-fluid coupling in porous medium. In this paper, continuity equation of hydraulic fracturing fluid seepage and stress equilibrium equation of rock deformation are established, the criterion for fracture initiation of quadratic nominal stress and fracture propagation of critical energy release rate is introduced, horizontal flow and vertical flow of fluid along fracture is considered, and the Soil module in finite element tool ABAQUS is applied to stimulate 3D composite fracture initiation and propagation in hydraulic fracturing. The cohesive element is used to pre-define the fracture path, and the corresponding user subroutines are also developed and embedded into ABAQUS to determine the initial in-situ stress field, seepage field, depth-dependent porosity and time-related loss coefficient. The result of numerical simulation can show fracture geometry, fluid pressure distribution along fracture, rock deformation and stress distribution, pore pressure distribution and fluid loss at different time points of pumping in hydraulic fracturing. Apart from that, the influence of fluid properties, volume, interlayer stress difference and loss coefficient on fracture geometry is analyzed. [ABSTRACT FROM AUTHOR]

The air driving is a promising clean and efficient new technology to improve oil recovery. In this paper, considering the properties of some light oil reservoir fluids, experimental studies on oxidation between light crude oil and air were carried out under the condition of low temperature and high pressure. The results indicated that oxidation reaction can greatly reduce the oxygen content in the air to a safe range. The reaction generated some kinds of new production such as CO2 and aldehydes, meanwhile cracking phenomenon occurred on intermediate hydrocarbon. The cracking light hydrocarbon, N2 of air and self-producing CO2 showed strong extraction capacity to the crude oil under the experimental condition. [ABSTRACT FROM AUTHOR]

As in-depth profile control and oil displacement agent, polymer microspheres have achieved good effects. However, microspheres has limitations in sphere of application. In this paper, new absorbent quadripolymer resin microspheres were designed and synthesized by acrylamide, bisacrylamide, acrylic acid and butyl acrylate, and the particle size and plugging performance of resin microspheres were studied. Performance evaluation test shows that the synthetic resin microspheres are of micron magnitude of particle, large quantity and moderate sphericity; the higher the temperature is, the greater the swelling rate will be, and the higher the mineralization is, the lower the swelling rate will be. The solution viscosity of resin microspheres is in inverse proportion to temperature and in direct proportion to concentration. Under the condition of 60®C and the concentration of 3000 mg/L, the viscosity of the microspheres solution is not high and presents shear-thinning characteristic, which ensures a good ability of injection. The core plugging experiment shows that the microspheres can plug medium to high-permeability oil reservoirs effectively with a plugging ratio of 80%-90 %. The resin microspheres have a potential value in field application, and we can proceed with the size optimization and strength optimization in order to meet field requirements. [ABSTRACT FROM AUTHOR]

Such as side attrition of pumping rods and tubes problems often encountered when the conventional oil pumping unit is used for inclined wells production. To solve the technical problems, a new liquid power assisted rodless oil pumping system is developed based on hydraulic principle. The novel system can completely solve the rod-tube side attrition problem, and is especially applicable used in inclined wells. This system includes ground hydraulic driving system, power transmission system and down-hole hydraulic oil pumping system. Its workflow is introduced in this paper. In-site test has smoothly run over 18 months which indicates the system can fully meet the oil field production requirements. [ABSTRACT FROM AUTHOR]

The dynamic analysis and fault diagnosis of ESP well are critical section of ESP wells' management. The results of conventional working condition analysis with current card, production performance and well history are not accurate. By providing the ESP with a downhole tractometer, real-time recording of unit operation parameters is realized, which provides more and visual information for dynamic analysis and fault diagnose, thus comprehensive and correct analysis of working condition can be performed to find out fault causes and further to tap oil well potential. This paper summarizes the types of ESP fault in a simple way by in-depth analyzing and plotting the ESP tractometer data. Field application shows that the above analysis method is a preferred way and worth popularizing. [ABSTRACT FROM AUTHOR]

Yong'an block of Shengli Oilfield is a typical small complex fault block oil reservoir. In order to explore the potential of this kind of reservoir further, a cross-block ladder horizontal well is used on the basis of recognizing faults, and the remaining oil in different faults is produced by one well. By this method, the recovery is improved and the drilling cost is decreased. The paper analyzes the reservoir characteristics of Yong'an block and illustrates the difficulties for drilling and completion of this well, on the basis of which it introduces the drilling and completion techniques of the first cross-block ladder horizontal well of Shengli Oilfield, Well Y3p9. Geosteering technique and seismic cross section are combined to determine the fault location and to accurately control the well trajectory to pass through faults and dig into another oil layer. Drilling and completion integrated technique and plastic micro-expansion slurry are taken to greatly increase the cementing quality of ladder horizontal wells. This well has been successfully drilled and produced, which proves the cross-block ladder horizontal well can improve the recovery ratio of fault block reservoir, and has promotional value. [ABSTRACT FROM AUTHOR]

Long lateral-section horizontal wells play an important role in exploiting oil and gas reservoir. Compared with vertical well and general horizontal well, it has unparalleled technical advantages. However, because of some factors such as long lateral-section, complex rock lithology, and long contacting time by drilling liquids or drilling tools and formation, many technical problems rise in the process of drilling and cementing. To raise the drilling level of long lateral-section horizontal wells, the paper summarizes these problems firstly, and analyses the reasons of drilling and cementing difficulties secondly. It concludes that the drilling difficulties of long lateral-section horizontal wells are caused by the long lateral-section, and the cementing difficulties are mainly caused by the status of horizontal-section being vertical or approximately vertical to the gravity direction of pipe and slurry. Finally the paper proposes some measures such as optimizing well trajectory, optimizing the performance of drilling liquids and cement liquids, optimizing drilling and cementing tools, and optimizing the tripping method of casing, which raises the quality of drilling and cementing and brings some guidance on the drilling and cementing of long lateral-section horizontal wells. [ABSTRACT FROM AUTHOR]

Optimization model of ICD in horizontal wells coupled with the reservoir and different types ICD computation model of pressure difference were built in this paper on the basis of analyzing the flow process of fluid from layers to wellbore under the condition of well completion design with ICD in horizontal wells. And then, static simulation parameters design method and dynamic simulation parameters design methods of ICD in horizontal wells were studied, and then the characteristics, differences and operation of these two types design methods were elaborated respectively. On this basis, optimal design about ICD in horizontal wells was figured out by combining both the static and dynamic stimulated parameter design methods. The feasibility and applicability of model and optimal design method of well completion with ICD in horizontal wells were verified by example calculation and analysis. These study results provide some theoretical basis for optimal design about ICD of horizontal wells. [ABSTRACT FROM AUTHOR]

The low permeability difficult-to-produce reserves and unconventional oil and gas reserve in Dagang oilfield is rich, and horizontal wells with staged fracturing completion technology is probably the mainly mean to economically and efficiently develop these reserves. In order to analyze the applicability of staged fracturing in horizontal well completion technology in Dagang oilfield, application trials of openhole packer staged fracturing completion, casing cementing sliding sleeve staged fracturing completion technology and hydraulic jet perforation completion with immovable string were conducted to form a new well completion technique, which take the casing cementing and sliding sleeve subsection fracturing as the main technology. The newly process has the advantages of integrated pipe column for well cementing, completion and staged fracturing, full size and fracturing operation continuous, which can shorten the working period and sliding sleeve can be closed for water blocking point in late water-producing layer. Meantime, there also presents some problems with this technique such as wellbore production plug caused by ball dropping, poor cementing quality because of rubber plug no pressure and adjacent wells connection. Aiming at the existing problems, analysis and evaluation were conducted, and solutions were proposed in this paper. Field application primarily realized normal production of oil wells, which provides foundation for the further scale application of the similar staged fracturing completion technology. [ABSTRACT FROM AUTHOR]

The mechanism of deep penetration of radial well with hole-drilling in casing technology developed in recent years is to form a plurality of radial hole in reservoir through high pressure water jetting, which could enlarge the drainage area and reduce production pressure drop. This paper analyzes the technical principles of this technology, and then proves the mechanism with well and layer selection of test wells through technical applicability. On the basis of these, the radial hole design plan of two testing wells were proposed, and the on-site operation situation was illuminated from the aspect of field test preparation and construction techniques. The testing results showed that both wells site construction had met the requirement of the design and made the yield increasing effect at some certain degree, even though failed to achieve the anticipated capacity. It is thought that the sand blocking resulted from debris flowback difficulties is the key reason for increase of output not enough during the radial water jetting process. [ABSTRACT FROM AUTHOR]

Changshaling Structural Belt is an important oil and gas exploration area in Jiudong Basin, and abnormal high pressure is universal in the zone. The paper proposes a new three-dimensional (3D)pore pressure calculation method based on single point hypothesis, which can use 3D interval velocity data to estimate 3D pore pressure. The novel method was applied to the 3D pore pressure calculation and analysis of Changshaling Structural Belt. Firstly, the pore pressure profile and model parameters of several key exploratory wells were established. Secondly, the 3D interval velocity data of the structural belt was obtained by seismic inversion. Further, the computer program was developed, and it was used to calculate the 3D pore pressure of Changshaling Structural Belt. Finally, with the 3D pressure results of Changshaling Structural Belt, the pore pressure distribution of this zone was systematically analyzed, with positive results. [ABSTRACT FROM AUTHOR]

To improve the effectiveness of network fracturing, this paper details the disadvantages of the wax balls as blocking material, and they are reducing pumping efficiency, not having enough strength and reducing the fracture conductivity. Based on the proppant conductivity test, the blocking fracturing using large size proppant was recommended, and it has been applied in 15 layers of 9 wells. In addition, TSO fracturing also has been field tested in 1 layer. The analyses after fracturing show that both the two methods improve the fracture net pressure effectively. The oil production of first three months is 101.2%, 103.8%, 133.3% higher than that of adjacent wells, so the technology is one of effective ways in which make low/extra low permeability be developed economically. [ABSTRACT FROM AUTHOR]

The horizontal wells in low permeability tight sandstone gas reservoirs of Sugeli were featured by multiple layers, long gas-bearing section and poor physical properties, so open hole packer staged fracturing is an effectively measure to enhance single well gas production. The key points of hydraulic fracturing for tight sandstone gas reservoirs are mainly improving reservoir percolation capacity on the plane and increasing the producing degree and validity of reservoir profile in the vertical, and there is an obviously positive correlation between stimulated volumes of reservoir and yield increasing effect. Volume fracturing mode adaptable to open hole horizontal well of Zone Su53 was investigated, and then this paper proposed the technique and realize method of multiple crack volume fracturing. Great stimulation effect in field has established a new technique thought for high efficient development of Sugeli gas reservoir. [ABSTRACT FROM AUTHOR]

In order to gain stable single well production rate, this paper provides a method to effectively control the natural decline rate and proposes the way to realize it. Taking continuous flow process of fluid as main line, three zones, two types and six factors analyzing methods were mentioned in detail. Preliminary analyses were made to the target parameters of each flow zone and the component part of each factor affecting the target. It is suggested that gray correlation theory was used to investigate the correlation degree between the influence factors in every flow zone and zone target. Priorities of control and adjustment measures could be chose according to the sequence of correlation degree for influence factors. [ABSTRACT FROM AUTHOR]

For deeply buried and high formation fracturing pressure of deep water ultra deep reservoir, it is difficult to break the rock stratum and the pressure-bearing requirements for fracturing equipment and pipe strings are extremely high. So fracturing operation in deep water reservoir always faces high construction pressure and high risk, meanwhile, the limited space makes it difficult to equip large fracturing equipment on offshore platforms or operating support vessels. In order to minimize the construction scale, reduce wellhead injection pressure, this paper discussed an autogenetic heat and high temperature resistant high-density fracturing fluid system, and then performance evaluation in the laboratory and in-situ friction measurement were conducted for this new fracturing fluid system. The experiment results show that the density of fracturing fluid was 1.5 g/cm³, and friction reducing rate can reach to 59.6% with temperature resistant of 140 °C.Introduction of autogenetic-heat system has greatly shortened the breaking time of fluid and the associated gas could promote fracturing fluid flowback after gel breaking. [ABSTRACT FROM AUTHOR]

An analytic solution of calculating the distance between measurement point and formation boundary using natural gamma flux was given in this paper based on infinite uniform horizontal strata model. Building mathematical model with the spherical coordinates, it is assumed that the probe points are ideal points, and the stratum is similar to horizontal infinite uniform model. The analytical solution form is very simple and easily programming analysis to improve efficiency, and can be developed to separate calculation module which could called for other programs. It also has certain reference value for analyzing techniques such as geologic steering, LWD logging data post-analysis and stratigraphic boundary determination. The model still has space to improve, such as orientation and thin strata identification; besides, further analysis and investigation are also need to make sure the technique being applied in practice as soon as possible. [ABSTRACT FROM AUTHOR]

Due to the derrick substructure non-uniform subsidence of Well KXS203, casing head and wear bushing of this well were severely worn during drilling, and then casing string leaked later in pressure testing. In order to figure out the cause of wellhead equipment worn, and to prevent this kind of accident from happening again, the paper gives an investigation on the wearing condition of wellhead equipment and drill pipe, and calculates the eccentric wellhead degree due to derrick foundation settlement, and analyzes the influence of dimension match between drill pipe tool joint and wellhead equipment, wellhead eccentricity, performance of wear bushing and jacking screw, rotation of the drill string, drilling trip, and rotational speed of the drill string on wellhead equipment eccentric wear. It is considered that the wellhead worn is related to all above aspects, but the wear of wellhead in this well is mainly because of the wellhead eccentricity and wearing bush failure. Some measures are suggested to prevent well head equipment from wear. [ABSTRACT FROM AUTHOR]

In the process of drilling complex wells, cutting bed occurs normally, and it always causes a lot of well hole problem, and affect the work efficiency badly. Now a kind of spiral tool is normally used to solve this problem, with some good application effect. By studying the migration process of cuttings through the basic configuration blades, the paper built a mathematical model, and found the influence of blade helical angle on cuttings transport velocity in tangential direction and axial direction. The results show that this kind of tool could accelerate cuttings effectively; as a controllable parameter, blade helical angle has important impact on application effect of the spiral tool; with the increase of the helical angle, cuttings tangential velocity increases and axial velocity decreases. Changing the helical angle could make the cuttings have a necessary velocity to be transported out of the hole efficiently. [ABSTRACT FROM AUTHOR]

In the late development periods of many oil and gas fields, reservoir pressure decreased to depletion, and the pressure coefficient would be reduced less than 0.4. Formation pressure reduction would result in in-situ stress changes and cause the influence on wellbore stability in drilling. Based on the influence of pressure depletion on reservoir in-situ stress and stress distribution around the wellbore in depleted reservoir, this paper analyses the effect of pressure depleted on wellbore stability of directional wells. Calculation results shows that there is a neutral angle in depleted reservoir drilling, when inclination angle is smaller than the neutral angle, the safety window of drilling fluid density will become wider, and when inclination angle is larger than the neutral angle, the safety window of drilling fluid density will become narrower. The neutral angle has no relationship with the level of pressure depleted, but has relationship with azimuth angle, and keep inclination angle below the neutral angle and away from the azimuth of maximum horizontal principle stress is beneficial to drilling safety. It provides a reference for drilling designing in depleted reservoirs of different periods. [ABSTRACT FROM AUTHOR]

The main reason causing clay shale formation wellbore instability is that the expansion and sloughing of clay shale after water absorption. The thought was proposed that silicon dioxide nano-particles was used to plug the nano-size pores and throats of shale to reduce the permeability of shale, resulting in decreasing and delaying water invasion into shale. On the basis of preliminary studies, the paper evaluated the improvement effect of three types of drilling mud with two brands of silica nano-particles at different temperature, by means of transmission electron microscopy analysis, regular performance test of drilling fluid and scanning electron microscope analysis. Results show that silica nano-particles could effectively reduce the filtration of Fresh Water Mud (FWM) and Bentonite Mud (BM) with temperature increase. It could reduce the loss of water by 56.25% at room temperature and 78% at 140 ℃. It has little effect on Low Solid Mud (LSM). Finally, to the drilling mud with the weight concentration of 10% had better plugging capacity than that with the weight concentration of 5% because of forming more continuous and tight mud cake. Based on the experiment results, FWM and BM's filtration properties could be improved using nano-particles with temperature increase (from room temperature to 160 ℃). [ABSTRACT FROM AUTHOR]

In order to improve mature single well production and speed up the curing process of casing damaged wells with casing diameter of Ø146 mm, it is decided to use the reaming tool to increase the diameter of completed wells, and to increase cement sheath thickness, furthermore, to improve well service life. In this paper, the completion of Well Z3034 is designed and optimized from three aspects, completion method, completion fluid and borehole reaming. The working process of reaming and completion string tripping are introduced in detail, the success of the well completion provides a feasible way for subsequent treatment of slim-hole casing damaged wells in Redbai oil field and conducting of slim-hole sidetracking. The production of Well Z3034 has been relatively stable since the start of production, with the average rate of 5t/d, and it is 5 times of the non-sidetrack case. [ABSTRACT FROM AUTHOR]

Deep-water heavy oil is an important marine petroleum resource. Due to the low temperature in deep water, the mobility of the heavy oil is low, leading to difficult development. Based on the development situation of the heavy oil industry in China and the experience of the successful cases of deep-water heavy oil development overseas, the paper summarizes the main developing technology and method of the deep-water heavy oil development in aspects of key facility, artificial lift equipment, drilling & completion technology and flow assurance method, and analyses the experience of Petrobras in developing Campos Basin deep-water heavy oil field. The conclusion is that by using reasonable secondary recovery, artificial lift and flow assurance technology, the deep-water heavy oil projects can be beneficial and promising. The paper gives some exploratory viewpoint and suggestions, which is of important value to exploit the deep-water heavy oil development technology. [ABSTRACT FROM AUTHOR]

Water/gas-yielding rules in the water-drive gas reservoir become complicated after water breakthrough, which results in the increasing difficulty of the water-drive gas reservoir development. At present, there is no mature and effective dynamic analysis method in developing the water-drive gas reservoir. Based on the gas-water two-phase flow law and the material balance equation, the water-drive characteristic curve of water-drive gas reservoir was developed in this paper, in which the cumulative gas production is in logarithmic relation with gas-water ratio, and in linear relation on semi-logarithmic coordinates. And the dynamic control reserve of gas well after water breakthrough can be inversely calculated by the slope of the line. By the application on a certain gas field, the research results were proved to be able to effectively predict the gas wells development performance and the dynamic control reserve variation during development. And it is of great significance to the development of water-drive gas reservoir. [ABSTRACT FROM AUTHOR]