Optimal Design Of Wellbore Trajectory For The Bashijiqike Formation In The Keshen Region Based On Rock Mechanics

The Kuche Depression in the Tarim Basin is quite rich in oil and gas resources,and has huge potential for natural gas resources.The Keshen region has become the main production area for increased reserves and production in the Tarim Basin.The burial depth of the Bashijiqike Formation in the target layer is 6000 m on average,which leads to high single-well mining costs.It is necessary to use high-angle wells to increase single-well production.Due to the deep burial of the reservoir,in the environment of high temperature,high formation pressure and high in-situ stress,The wellbore stability of wells with large slope is poor,and complicated situations occur frequently.Therefore,the research on the engineering geomechanical characteristics of Keshen Reservoir was carried out,the characteristics of reservoir fractures,rock mechanics and in-situ stress were analyzed,and the rock mechanics and wellbore stress distribution model of the block were established.And based on this,an optimized design of wellbore trajectory that takes into account safe drilling and high-efficiency fracturing.Undertake the following main tasks:(1)Research on engineering geological characteristicsBased on the geological data of the Keshen region,it is concluded that the geological conditions in this area are complex,and the reservoirs are fractured and tight sandstone with low porosity and permeability.Analyze the sandstone characteristics of the reservoir from a microscopic point of view,select the sandstone debris of the target formation to determine the mineral composition of the whole rock,determine the content of various clay minerals in it,and observe the development of microscopic fractures of the mineral by scanning electron microscope.Obtain the sandstone core and logging data of the reservoir,identify and count the fractures in the target formation,and accurately describe the occurrence characteristics of the fractures.(2)Rock mechanical characteristics and in-situ stress characteristicsCarry out high temperature and high pressure triaxial compression experiments.and establish sandstone failure criteria under temperature and pressure conditions;Based on the relationship between rock mechanics parameters and indoor P-wave velocity,establish a rock mechanics parameter calculation model that matches the target layer,Use the continuous curve of rock mechanics parameters to analyze the change law of rock mechanics parameters of the target layer;The relevant instruments are used to measure the in-situ stress characteristics of the region to provide a basis for the drilling orientation optimization.(3)Optimal design of wellbore trajectory considering wellbore stability and efficient hydraulic fracturingEstablishing the wall stress distribution model of the target formation with highslope wells and analyze the stress distribution characteristics around the well;In order to determine the temperature and the influence of the weak face on the stability of the wellbore,establish the fracture criterion of rock formation under fractured and high temperature conditions;In-depth study of the relationship between artificial cracks and natural cracks,to determine the expansion of the two cracks after meeting;Determine the superior orientation of fracture development and the lower orientation of collapse pressure,taking into account safe drilling and efficient fracturing,and optimize the wellbore trajectory of the region.(4)Optimal design of high-slope wellbore trajectoryAnalyze the drilling data in the application region,Determine the fracture characteristics,in-situ stress characteristics,and pressure-bearing capacity of the target layer of the region;Then take into account efficient fracturing and wellbore stability to determine the dominant drilling azimuth.Apply it to the region to obtain better engineering implementation results.