The accurate prediction and improvement of the maximum measured depth (MMD) of horizontal extended-reach well (ERW) play a major role in improving the economic benefits and avoiding drilling risks of horizontal ERW in Fuling shale gas, China. In this study, a model to predict the MMD of horizontal ERW is presented, and the MMD of Jiaoye 2-5HF well in Fuling Shale Gas is determined. The MMD prediction model is established based on the dynamic pressure balance of bottom hole and the restriction of drilling pump. Considering the bearing capacities of drilled formation and drilling pump, this paper predicts the MMD, especially the horizontal-section limit of Jiaoye 2-5HF well in Fuling shale gas based on the extended-reach limit theory, determining whether it can meet the drilling need of 3000m horizontal section. The results show that the well's MMD is 6928m, and the horizontal- section limit is 3985m according to the casing programme and drilling parameter of Jiaoye 2-5HF, which can meet the drilling need of 3000m horizontal section. The MMD first increases and then decreases with the increase in drilling fluid flow rate. In addition, the Jiaoye 2-5HF well cannot meet the drilling need of 3000m horizontal section when the drilling fluid flow rate is greater than 38L/s or the rated pressure of drilling pump is less than 23.5MPa. Furthermore, the constraint conditions for the extension ability of horizontal ERW under different drilling parameters are not the same, and the MMD values are also different. Therefore, it is necessary to calculate separately. This work provides a practical tool for predicting the Jiaoye 2-5HF horizontal well's MMD in Fuling shale gas. The study is significant to avoid drilling hazards, maximize reservoir contact and obtain good economic benefits of Fuling shale gas in China.
Trajectory design of sidetrack horizontal well is faced with bypassing obstacles in cluster wells which makes the design process more complicated. The obstacle is assumed to be drilled trajectory sections such as vertical section and directional section, then they are described as a part of cylinder and annulus. Trajectory type for bypassing obstacle is classified based on geometrical relationship between tangent line of sidetrack point, tangent line of target point and axis of obstacle. The objective function is minimizing the total trajectory energy and the constraints include the safety distance to obstacle and the maximum build rate and maximum turn rate. Teaching-learning Cuckoo Search algorithm has been proposed to solve the established model. Case studies have been carried out according to different trajectory type, the results indicate that the proposed method can obtain sidetrack trajectory with minimum trajectory energy, in the meanwhile, the trajectory can avoid collision with obstacle and the wellbore curvatures are appropriate, the new method avoid trial calculation, it is also applicable to other types of sidetrack well trajectory for bypassing obstacles.
Accompanied with the widespread application of complex wells such as cluster wells in the exploitation of oil and gas resources, it is becoming more and more important to reduce or accurately describe the size of the wellbore position uncertainty as much as possible. It is well known that axial magnetic interference affects azimuth measurement. In this paper, the correction method of axial magnetic interference in azimuth measurement and uncertainty ellipsoid calculation method considering axial magnetic interference correction are introduced, and the influence of axial magnetic interference correction on the position uncertainty of a horizontal well is analyzed through an example. The research shows that the influence of axial magnetic interference on wellbore position measurement error varies with measurement depth, and axial magnetic interference plays an increasing role in the influence of wellbore position measurement error. Therefore, well trajectory should be measured in an environment free of axial magnetic interference.
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