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For the layered reservoirs such as shale, the anisotropic mechanical properties exhibit variations in elastic modulus and tensile strength, both of which are factors influencing fracture initiation...

Branch wellbore fracturing in branch wellbore is a new technology for developing unconventional oil and gas reservoirs. In this study, we developed a 3D numerical model based on finite element meth...

The application of segmentation technology in CT images can not only retain the clear characteristics of CT images, but also have the advantages of high resolution, clear anatomical relationship and clear pathological development. Level set segmentation method combines region and boundary information to solve the problems on complex texture and blurred edge of CT image. Therefore, this paper proposes an algorithm for regional growth and level set interaction for the problem of boundary sensitivity and lack of regional information in level set segmentation. In order to improve the efficiency and reduce the error of segmentation, this algorithm uses Gaussian filter to remove noise. Meaning while it adopts Ostu method to transform the image into a binary image. In addition, this algorithm provides an ideal growth environment for the seed point of the region growing algorithm correspondingly. The results of region growth are accomplished as the initial contour of the level set to modify the initial boundary. The boundary indication function introduces the region information; the level set segmentation algorithm achieves the purpose of accelerating in the pixel similar region and stopping at the target boundary as a result. Comparing the overall improved algorithms with the previous both region growing method and the level set method, the experiment results shows convincingly that the interaction between the level set segmentation and the region growing reduces the number of iterations. Under the condition of weak boundary and high noise, the boundary indicator function can accurately and completely segment the organ region and save the details of the internal organ completely, which improves the segmentation accuracy to a certain extent.

Medical images are difficult to observe due to blurred organ and tissue boundaries and uneven grayscale in the area, which interferes with the diagnosis of the disease. In this paper, a level set segmentation method combining information is proposed for the redundant effect caused by the segmentation of organ tissue in a complex environment. Simulation results show that, when the improved algorithm is used to segment medical images with blurred borders and uneven grayscale, although it requires a lot of calculation, it obviously sup- presses the redundancy effect and improves the accuracy and efficiency of the segmentation algorithm.

Radial drilling-fracturing, the integration of radial drilling and hydraulic fracturing, is an innovative approach to develop low permeability, thin target layer and naturally fractured reservoirs, etc. Understanding the fracture initiation process is required in the practical application to avoid high fracture initiation pressure (FIP) and complex fracture geometries near the wellbore. In this paper, we develop an analytical model to determine FIP, location of rock failure zones and initial fracture direction from the radial lateral borehole. This model is based on the stress superposition induced by cased main wellbore and radial borehole, and the maximum tensile stress criterion is adopted. Then, we perform a series of sensitivity analysis by examining different effects of in-situ stress regime, lateral orientation (the included angle between borehole axis and maximum horizontal in-situ stress), lateral length, and lateral diameter. Besides, the effect of pre-existing weakness plane, across which the tensile strength is much lower than that of the intact rock, is also investigated, when the plane is drilled through by the radial borehole. Results show that for intact rock with no weakness plane, the in-situ stress regime and lateral orientation are main factors influencing FIP, location of rock failure zones, and initial fracture direction. Under the in-situ stress regime of normal fault, fracture initiates vertically, and FIP enlarges as lateral orientation increasing; under the in-situ stress regime of strike slip, fracture initiates vertically with small lateral orientation, while fracture initiates horizontally with large lateral orientation; and under the in-situ stress regime of reverse fault, fracture initiates horizontally with any lateral orientation, and FIP decreases as the lateral orientation increasing. It is also found that when the fracture initiates vertically, the location of rock failure zones is at the base of radial borehole on its top and bottom sides; and when the fracture initiates horizontally, the location of rock failure zone is at the remote region of radial borehole on its right and left sides. The lateral length has a minor effect on fracture initiation, and the influence of lateral diameter is negligible. When the weakness plane is drilled through by the radial borehole, fracture initiation pressure from weakness plane is affected by its occurrence, i.e., azimuth and inclination. FIP is determined by taking the minimum between fracture initiation pressure from rock matrix and the weakness plane. The key findings of this work could provide critical insights into understanding radial drilling-fracturing initiation characteristics.

Fiber containing power law fluids are widely used as drilling/fracturing fluids to improve wellbore cleaning efficiency or enhance proppant transport in the oil and gas industry. Understanding the settling behavior of solids in fibrous fluids is critical for designing and optimizing fiber containing fluids. In this paper, an new equation for predicting the settling velocity of solids in fiber containing power-law fluids is presented. Settling tests recorded by a high-speed camera were conducted, considering fiber concentration, sphere diameter, particle density and base fluid rheology. The microscopic observation shows that numerous filaments disperse in the base fluid, intercross together, and form the fiber network. The fiber network causes a minor change in the base fluid rheology, and reduces sphere settling velocity by exerting the mechanical drag, called fiber drag force to the settling sphere. To quantify the fiber drag force, a revised definition of the fiber drag coefficient is made and proved to be fit for spheres with different densities. The sum of fiber drag coefficient and viscous drag coefficient is called as total drag coefficient. A non-dimensional term that is the function of total drag coefficient is defined that is independent of the sphere settling velocity. Finally, the settling velocity equation is obtained by correlating the non-dimensional term versus the particle Reynolds number (0.002–416), fiber concentration(0.02%–0.10% by weight) and flow behavior index. The predicted settling velocity is in good agreement with the measurement, with an average relative difference of 12.49%. The key findings of this work are expected to provide a basis for better the application of fiber containing power-law fluids.

Because of daily life natural or unnatural accidents, the Vehicular Ad-Hoc Network (VANET) is one of the affecting areas for the enhancement of Intelligent Transportation System (ITS) for facilitating road safety, traffic management and entertainment services for drivers and passengers. Vehicular networks can help avoid accidents by warning drivers of forthcoming risks or prompting embedded systems to respond autonomously. Multi-hop wireless connectivity and frequently changing network topology in VANET are the factors to plan effective and efficient dynamic routing protocols. While these studies are anticipating, designing protocols for vehicular networks has many challenges. The current routing protocols for VANET are not sufficiently effective to meet all traffic situations. Therefore Creditable routing protocols are required to start correspondence between vehicles in future for passengers and road security and safety. This paper demonstrates literature study related to some of the Topology-based investigated VANETs routing protocols in the light of premise of their characteristics and operations and additionally their qualities and shortcomings. Furthermore a few proposals are made to accomplish change in execution of these protocols.

At present, the informatization construction of Small and Medium-sized Enterprises (SMEs) in Anhui province has embarked on the path of rapid and healthy development. The audit environment that the auditors are faced with is also changing along with it. This will inevitably affect the transition of audit objective, audit object and audit approach, and it also places greater demands on auditors. For this reason, innovations are required in risk-oriented audit of SMEs in order to adapt to the new situation.

Presently under the circumstances of tight-money policy, numerous corporations are facing the issue of the shortage of cash flow, including real estate industry. Strained capital chain gets the real estate industry to gradually droop. The author thinks that there’s some vitality behind the drooping appearance and corporations should live through this difficult time by expanding the sources of money.

To simulate the human decision-making in steering to follow a planned path, we modeled the driver’s learning process by using an idea of target position. The proposed model dealt with the driver’s decision-making mechanisms in tracking a target position by means of Cloud Neural Network. Results from the simulation of lane changing showed the capability of the proposed model to simulate a driver’s steering behavior with emphasis on learned skill.