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The reuse of existing well bores is a cost-saving technique used by oil and gas producers in mature fields. This process usually requires the removal of tubing and packers to allow the well to be deepened or sidetracked. The tubing removal process is often made difficult when the tubing is stuck inside the casing because of mechanical binding or binding caused by dehydrated mud or sand in the annulus between the tubing and casing. Conventional direct and indirect methods of finding the stuck point(s) along an interval of tubing, such as free-point indicator tools or acoustic attenuation measurements, have proved themselves useful in finding the point(s) where the tubing is stuck. However, when the sticking is caused by uncompacted sand that has entered the annular space between the tubing and casing, these conventional stuck-pipe indication methods are often inconclusive or misleading. Technological advancements in the design and development of slim, 1 11/16-in, outside diameter (OD), radial cement bond tools allow the application of a new measurement to find sand-stuck tubing intervals. These tools provide up to six independent, closely spaced acoustic attenuation measurements distributed radially around the tool body. When the recording operation is performed inside the tubing, the increased sensitivity of these tools to sound attenuation, as compared with conventional omnidirectional amplitude signals, allows sand intervals along the outside of the tubing to be distinguished from intervals where little or no sand is present. This information is used to select the best depth to sever or back-off the free tubing in order to reduce the interval length and expense associated with the washover process required to remove the remaining tubing from the wellbore. An overview of conventional stuck-pipe recovery techniques is provided here, along with a brief explanation of applicable acoustic technology. A case study of a South Louisiana well is presented to demonstrate the application and illustrate the cost savings which can be gained by use of this very new technology. [ABSTRACT FROM AUTHOR]

The article describes the development of a new collapse-strength equation for oil-country tubular goods. The new model is evaluated through comparisons with both finite-element analyses and test data because it is more accurate in dealing with combined internal pressure, external pressure and axial load. The model presented is recommended is for developing design collapse strengths in the new ISO TR 10400 standard of 2006.

The article provides information on the new portable casing-running system that facilitates mechanizing the casing-running process. The new technology eliminates potential safety hazards, provides assurance that the casing can be run to the intended casing point, offers the ability to ream casing to bottom, reduces personnel requirements for running cases and eliminates the need for a stabber in the derrick.

The article presents a study that evaluated the impact and management of casing deformation caused by tectonic forces in the Andean Foothills, Colombia. The research assessed the impact of the deformation on well integrity and developed a strategy for managing the consequences to achieve improved business and operational decision making. More information could be found in the article.

In eddy-current nondestructive testing of conductive tubes such as oil-well casings, the measured tube wall thickness and inner diameter must be compensated for variations of electromagnetic properties of a tube material-magnetic permeability and electrical conductivity. Commercial systems for eddy-current nondestructive testing of oil-well casings incorporate multiple coils and multifrequency excitation for measurement of the inner diameter and the electromagnetic properties. This paper investigates the feasibility of the electromagnetic properties and inner diameter measurement with only one coil excited at one frequency. The authors have derived a coil impedance model and developed an inversion procedure for the determination of tube properties. Measurements have been performed on several tubes made of different materials. In order to validate the model and the optimization algorithm, measurement results were compared with the predictions of the model and finite-element analysis. Applicability of the method has been confirmed for the investigated frequency range (1-50 kHz). [ABSTRACT FROM AUTHOR]

The article studies geostopping with resistivity-forward modeling to prevent drilling into the lost circulation zone of a prolific carbonate reservoir. The traditional well design dictated that before entering the reservoir, a casing had to be installed to stabilize the hole in soft shale. The uncertainty of detecting the formation top resulted in a premature casing commitment of at least 30 feet true vertical depth above the top of the reservoir and the need to use an expanded liner to cover 300 feet of exposed shale above the reservoir.

Discusses the successful use of a unique cementing system and a circulation method in the cementation process of one casing string in a relatively shallow geothermal well in central California and a relatively deep string in central Wyoming. Advantages and challenges of the reverse-circulation placement technique; Use of the foamed calcium aluminate blend cement.

Describes specialized equipment and techniques that have been developed to allow directional drilling with casing. Casing while drilling (CwD) process; Retrievable downhole tools; Directional CwD system testing.

Formation analysis from behind casing is gaining more relevance in assessing reservoirs, not only in aging fields but also in new wells completed either without the full complement of openhole petrophysical measurements or with openhole measurements of inadequate quality. Before this technology was available, formation evaluation in freshly drilled holes was dependent on the availability of openhole log measurements. This paper discusses field examples in which reservoirs were evaluated without a full suite of openhole log measurements. Examples from two sidetracks in a mature North Sea field supported by water injection are presented. The small hole size limited openhole data acquisition to resistivity and gamma ray (GR) measurements, which were acquired using logging-while-drilling (LWD) technology. In both cases, pulsed neutron (PN) measurements were recorded through casing to augment the existing data. Porosity and formation sigma (macroscopic thermal neutron capture cross section) measurements were obtained. Fluid saturations were computed using this porosity and the LWD resistivity. Saturations also were computed from the carbon/oxygen measurement, and these agreed with the resistivity-based answers. Lithology analysis was performed using elemental spectral capture yields and was reliable and consistent fieldwide. The results show that, in a mature oil field, PN measurements can provide a complete lithology and saturation analysis in circumstances in which insufficient openhole petrophysical measurements are available. [ABSTRACT FROM AUTHOR]

Presents lessons learned from a tubing failure in the Marlin development in deepwater Gulf of Mexico, shortly after startup. Collapse of the production tieback casing; Description of factors affecting annulus pressure buildup and ways to mitigate the problem; Creation of an incident investigation team to evaluate the failure of Well A-2.

The results are presented for the experimental and theoretical investigations into behavior of casing string and cement ring of a well under the action of internal cylindrical charge explosion. It is shown that the developed calculation procedure can be used for analyzing the possible failure of well casing. [ABSTRACT FROM AUTHOR]

Presents a study on the combination of backfills and casual materials for access boreholes which will enhance the usefulness of neutron logging for environmental applications. Materials and methodology; Results and discussion.

Pulsed neutron logging tool (PNL), particularly small-diameter multifunction PNL, is an essential instrument used in casing well for evaluating residual oil saturation. In a borehole with a multiple casing string structure, PNL tools log in the oil tube and even the space between the casing and oil tube. Borehole/annulus holdup have a significant influence on the evaluation of oil saturation. Hence, the requirement of the estimation of borehole/annulus liquid holdup is highlighted. This study proposes a new method to determine the annulus oil holdup in a casing well with a complex string structure. For this method, the annulus holdup are derived from ΔS, which is defined as the difference between the relative variations of carbon/oxygen and carbon/hydrogen ratios. To demonstrate the feasibility of the proposed method, we first simulate the responses of ΔS under various borehole and formation conditions using the Monte Carlo method. The outcome shows that ΔS covaries with annulus oil holdup, confirming the feasibility of the proposed method in theory. The proposed method is applied to real data measured in an offshore production well. The result confirms that the formation water saturation calculated by the proposed method agrees well with the actual well production status, further confirming that the proposed method has a promising application in residual oil dynamic monitoring. • An algorithm is proposed to evaluate the annulus fluid holdup based on the Carbon/Oxygen and Carbon/Hydrogen ratios. • The Monte Carlo simulation is used to model the responses of RPM logging under various borehole and formation conditions. • The algorithm for evaluating the annulus fluid holdup is validated with simulation data and field logging data. [ABSTRACT FROM AUTHOR]

• We conducted a failure analysis of an N80 casing fracture in a certain well. • Large oxide-based metallurgical inclusions in the casing decreased its strength. • Suggestions are made to avoid such accidents in the future. An N80 casing in a certain oil well was broken. After the casing was pulled out, many cracks, sand holes, and corrosion and rust marks were observed in the casing fracture. To test the cause of the fracture, failure simulation using ANSYS software was carried out. Metallographic analysis test, chemical composition analysis test, and conventional mechanical performance test of the casing body were designed, and finally the failure analysis of the casing fracture was completed. The results revealed several large-scale oxide metallurgical inclusions in the casing near the upper end of the wellhead, which reduced the strength of the casing material and caused the casing to crack at the maximum stress position. In addition to harsh service environment, the casing was subjected to strong stress, which exceeded the strength limit of the casing and eventually caused the casing to break. The casing material met the standard requirements at all parts except the fracture areas. A calculation method is proposed for the ocean current and wind force; the method has high accuracy and can be used for analyzing similar offshore conditions. To prevent accidents, it is recommended to strictly control the heat treatment process of the casing material, optimize its microstructure, test its performance before deployment, and establish a real-time analysis system. Timely adjustments should be made to the operating schedule when operating in harsh environments. [ABSTRACT FROM AUTHOR]

• An online method for identifying the model structure and estimating its parameters. • The method is developed for Real-time Optimization (RTO) implementations. • Plant measurements and gradient are used for updating the model structure. • Problem is presented in a superstructure framework and solved using MINLP solvers. • A gas lift oil well network case study. The performance of model-based optimization methods, like Real-time Optimization (RTO), relies on the model accuracy and adequacy. However, features of the process may be unknown and/or the system behavior can drastically change with time (e.g. system degradation). Therefore, even if we have a perfect model in the beginning, we may end up making decisions based on a poor model. This paper proposes a method that adapts the model structure online, based on an available model component set, while simultaneously estimating the model parameters. The problem is presented in a superstructure framework and solved using a mixed-integer nonlinear formulation. Then, the updated model is combined with Output Modifier Adaptation, an RTO variant for economic optimization. Our method is tested in case studies considering a continuous stirred-tank reactor and a gas lifted oil well network. The results show that we can select the correct model structure, update its parameters, and simultaneously converge to the plant optimum. [ABSTRACT FROM AUTHOR]

Faced with severe corrosion of casing in oil wells, the epoxy coating was applied to prevent corrosion. Based on the mechanism that the filler eliminated the internal stress during the curing process of the coating and prevented the penetration of corrosive medium into the coating, a new filler was successfully prepared by the hydrothermal method. When the molar ratio of the precursor of ZrO 2 to MoS 2 was 1.2:1, MoS 2 was uniformly modified with ZrO 2 through mussel inspired chemistry of dopamine. Introducing fillers into epoxy coatings, specifically, a proper content of 0.8 wt.% filler can greatly improve the mechanical properties and corrosion resistance of the coatings. The coating maintained the excellent corrosion resistance for 16 h under high temperature (108 °C) and high pressure (pressurized with CO 2 gas of 35 MPa), which would provide us a reliable anticorrosive coating for oil wells metal casing. [ABSTRACT FROM AUTHOR]

It is difficult to implement treatment in slim hole wells because of the small internal diameter of casing, big limitation on tool selection and complexity and diversity of falling objects. Aimed at this, a series of fishing tools in slim hole wells was developed including oil pipe hoop back off sub, prevent channeling external hook and three adjustable ball overshot. The structure, operational principle, technique characteristics and field application cases of these tools were introduced in this paper. The application of these tools greatly enhanced the salvage success rate solved difficult problem of implement treatment in slim hole wells, which provide some technical reference for fishing in slim hole wells. [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]

Some production platforms have no spare slots to drill adjustment well in Bohai Bay, so it is proposed that some failure wells can be used to sidetrack adjustment wells. Sidetracking from production casing is impossible in some of the wells because of the small size, and it is necessary to sidetrack from surface casing, so it is necessary to retrieve production casing from wellhead to sidetracking point, which is cemented partly. One failure well has been taken as the experiment well to try to retrieve production casing. By designing and manufacturing special washover shoes and optimizing assembly of washover, the sections of production casing, which are concentric and slightly eccentric in surface casing, are washovered and retrieved. By designing and optimizing cutting pilot mill shoes and flat bottom mill shoes, the badly eccentric section of production casing is cut at a higher speed than by ordinary mill shoes. Finally the production casing is successfully retrieved, which meets sidetracking requirement. The technique makes a break in Bohai Bay and can be extended. [ABSTRACT FROM AUTHOR]

Well WEN13-STH305 is a dual-target side-tracked directional well, and the target zone is the middle stratum at the depth of 3700 m in the east of WEN13 block. Windowing was made inside the Ø139.7 mm casing, and the Ø101.6 mm liner was run, after which it is cemented, The side clearance at overlapping section is only 9.88 mm, and the density of drilling fluid is up to 1.78 g/ cm³, so the circulation loss and kick coexist in the section, with the great difficulty in cementing. It is currently the deepest sidetracked well with Ø139.7 mm casing in China. By conditioning mud property, testing of drilling tools friction and pressure bearing, optimizing liner hanger before running casing, and using the AMPS polymer filtrate reducer and intermediate temperature retarder, the free water and water loss have been controlled in high temperature slurry, and the problem of upper strength developing slow has been overcome. By the matching cementing technology, the cementing operation was made smoothly, and the CBL was with high quality. The successful cementing in this well provides a technical support for developing matured fields with sidetracked deep directional wells in ZPEB. [ABSTRACT FROM AUTHOR]

C110 oil well casing tubes should have high strength and corrosion resistance which is commonly used for deep wells operation containing corrosive media. In this paper, the microstructure evolution of a kind of semi-macro segregation originated banded structure in casing tubes is studied under different heat treatments. It is shown that the characteristics of the banded structure will change significantly in subsequent hot working and heat treatment processes. For the hot-rolled ones, the banded structure is composed of pearlite plus bainite. After quenching, it evolves into martensite band with high concentration solute elements. Finally, the banded structure will change into a carbide banding under the following tempering process. The temperature and cooling rate of the tempering practice show an obvious effect on the final band structure. To improve anti-SSC (sulfide stress corrosion cracking) performance, the favorable QT (quenching and tempering) practice for C110 steel should be a higher tempering temperature and a quicker cooling rate, from which the banded structure defects can be decreased together with an obvious improvement of the tube wall hardness uniformity. [ABSTRACT FROM AUTHOR]

The significant decreased wellbore temperature and increased casing pressure during fracturing fluid injection present a big challenge for the mechanical integrity of cement sheath in fracturing wells. Based on the theories of elastic mechanics, thermodynamics, and a multi-layer composed thick-wall cylinder, this paper proposed a new mechanical model of cement sheath for fracturing wells, coupling pressure, and thermal loads, which consider the failure modes of de-bonding, radial cracking, disking, and shear failure. The radial nonuniform temperature change and the continuous radial stress and radial displacement at two interfaces have been considered. With the proposed model, the radial distributions of failure stress and the corresponding safety factor for cement sheath during fracturing fluid injection have been analyzed and compared under four failure modes. Results show that the decreased wellbore temperature will produce significant tri-axial tensile stress and induce cement failure of de-bonding, radial cracking, and disking. The increased casing pressure will significantly lower the risk of de-bonding but also aggravate radial cracking and shear failure. For integrity protection of cement sheath, increasing the injected fluid temperature, maintaining higher circulation pumping pressures, and adopting cement sheath with a low elasticity modulus have been suggested for fracturing wells. [ABSTRACT FROM AUTHOR]

Geothermal energy has been used by mankind since ancient times. Given the limited geographical distribution of the most favorable resources, exploration efforts have more recently focused on unconventional geothermal systems targeting greater depths to reach sufficient temperatures. In these systems, geothermal well performance relies on efficient heat transfer between the working fluid, which is pumped from surface, and the underground rock. Most of the wells designed for such environments require that the casing strings used throughout the well construction process be cemented in place. The overall heat transfer around the wellbore may be optimized through accurate selection of cement recipes. This paper presents the application of a three-phase analytical model to estimate the cement thermal properties. The results show that cement recipes can be designed to enhance or minimize heat transfer around wellbore, extending the application of geothermal exploitation. [ABSTRACT FROM AUTHOR]