Deli Gao¹, Zhen Dong¹, Hui Zhang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.2, pp. 111-122, 2012, DOI:10.3970/cmes.2012.089.111

Abstract The bottom hole pendulum assembly is a type of bottom hole assembly (BHA) for controlling the hole deviation, and has been widely used in drilling engineering. Generally, the ability of the drill bit to penetrate laterally, is different from its ability to penetrate axially, so that the drill bit has an anisotropy which affects the hole-deviation-control characteristics of the BHA. The tilt angle and the side force of the drill bit are obtained by a BHA analysis based on the method of weighted residuals. Thus, the effective drilling force can be determined using the rock-bit interaction model. On this basis,… More >

Xuejun Hou^1,2, Deli Gao¹, Zhonghou Shen¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.2, pp. 97-110, 2012, DOI:10.3970/cmes.2012.089.097

Abstract Microhole drilling (MHD) is a new frontier drilling technology in which the diameter of wellbore is less than 88.9mm and coiled tubing (CT) is used as drill string. The CT wound around reel for MHD has small bending radius and large length to result in large circulating flow resistance and affect normal MHD circulation. The calculation model for curvature radius and length of CT wound around reel are established by analyzing the relationships among the various geometrical parameters of the reel system. The calculation model is combined with Dean number and power-law fluid state equation to put forward the calculation… More >

Jun Li¹, Shunji Yang¹, Boyun Guo^1,2, Yin Feng², Gonghui Liu^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.2, pp. 79-96, 2012, DOI:10.3970/cmes.2012.089.079

Abstract In the process of gas drilling, the mechanism of transport of the cuttings up the annulus is significant, because it controls the minimum amount of volume of the required gas, the cost of cleaning the borehole, the stability of the borewell and the drill pipe erosion, etc. However, current studies in this area are only limited to theoretical discussions. The reason why drill cuttings are of very fine sizes , in air drilling, is believed to be due to the repeated crushing action of drill bit at the bottom of the hole, and the collision between cuttings themselves and the… More >

Baohua Yu¹, Chuanliang Yan¹, Deli Gao^1,2, Jinxiang Li³

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 57-78, 2012, DOI:10.3970/cmes.2012.089.057

Abstract Shale is easy to hydrate and often causes a collapse of the borehole during drilling, especially in drilling extended-reach wells (ERW). In order to solve the problem of collapse of the shale, the changinges in the mechanical properties of shale, as affected by hydration and water absorption, are studied in this paper, through experiments. The relationships between the mechanical properties of shale and the water content are established. The borehole-stability models, which couple chemistry and mechanics are established, by considering the anisotropy of swelling, based on the experimental results. The stability of shale in the borehole is analyzed to obtain… More >

Cui Li¹, Deli Gao¹, Zhiyong Wu¹, Binbin Diao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 39-56, 2012, DOI:10.3970/cmes.2012.089.039

Abstract At present, a relief well is the most reliable method to control serious blowout accidents, and it is necessary to detect very accurately the relative position of the relief well and the blowout well. The detection tool should be capable of detecting directly the relative distance and direction between the relief well and the blowout well. Its detection accuracy should also meet the engineering demand of drilling a relief well. Using the working principle of a proposed detection tool, this paper analyzes the spread and attenuation laws of the current injected by a single-electrode or three-electrode array in the relief… More >

Fei Yin¹, Deli Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 25-38, 2012, DOI:10.3970/cmes.2012.089.025

Abstract The methods to design the casings used in oilfields, are currently based on the assumptions that the remote crustal-stress-field is axially symmetric, in plane strain. However, most of the failures of the casings are caused by non-uniform and asymmetric far-field crustal stresses, so that it is necessary for a proper design of the casings, to investigate and understand the casing's behavior under non-uniform far-field crustal stresses. A mechanical model is first established for the system, consisting of the casing and formation, by using the plane strain theory of linear elasticity. The non-uniform crustal stress is resolved into a uniform stress… More >

Zhaohui Xu¹, Deli Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 17-24, 2012, DOI:10.3970/cmes.2012.089.017

Abstract Little is explained about the process of casing window milling for sidetracking due to lack of analytical method for its mechanical characteristic. In this paper, 3D FE models are established using the commercial finite-element software ABAQUS/Explicit to make simulation analysis for two key stages of the process including the initial stage of casing milling and the stage of full-gauge casing window milling. The models involve the effects of main drilling parameters such as reaction force, torque, speed, feed rate per revolution, and milling angle. The calculation results verify the capability and advantages of 3D FE simulation for the process of… More >

Deli Gao¹, Feng Qian¹, Huikai Zheng¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 1-16, 2012, DOI:10.3970/cmes.2012.089.001

Abstract In deepwater wells for exploration and exploitation of oil & gas, the wellhead structure is of importance, and the annular pressure cannot be released after the casing hanger is set. The pressure changes in the casing annuli, caused by the temperature changes during the drilling and production processes, will increase the risk of failure of the casing. Therefore, a study of the safety of the casing in deepwater wells, by considering the complex engineering factors, will be of both academic as well as practical significance. In this paper, a model for the interactions among the casing-cement-formation system is established, by… More >

V. C. Loukopoulos¹, G. C. Bourantas²

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 531-558, 2012, DOI:10.3970/cmes.2012.088.531

Abstract Meshless Local Petrov-Galerkin (MLPG) approach is used for the solution of the Navier-Stokes and energy equations. More specific as a special case we apply the MLPG6 approach. In the MLPG6 method, the test function is chosen to be the same as the trial function (Galerkin method). The MLPG local weak form is written over a local sub-domain which is completely independent from the trial or test functions. The sizes of nodal trial and test function domains, as well as the size of the local sub-domain over which the local weak-form is considered, can be arbitrary. This may lead to either… More >

W.W. Zhang¹, Y.F. Nie¹, Y.Q. Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.6, pp. 507-530, 2012, DOI:10.3970/cmes.2012.088.507

Abstract A new algorithm for anisotropic triangular meshes generation in two dimension is presented. The inputs to the algorithm are the boundary geometry information and a metric tensor that specifies the desired element size and shape. The initial nodes are firstly distributed according to the above mentioned geometrical information, after bubble simulation, the optimized nodes set that meets the requirements of the metric tensor is obtained quickly. Then taking full advantage of the nodes set and the adjacency lists information provided by the process of node placement, a handful of non-satellite nodes are removed from the adjacency lists of the nodes… More >