Establishment And Application Of Three-Pressure Profile In Shuangyushi Structre Deep Gas Reservoir

The lithology of the sediments is dominated by carbonate rocks of Leikoupo-Qixia formation in ShuangYushi structure deep gas reservoir,Where the micro fracture is developed,the stress and the anisotropy are strong,also the multiple sets of pressure system exists on the vertical profile,because of which it belongs to the typical super deeper,high temperature,high pressure and high sulfur gas reservoir.During the drilling process,the wellbore collapse and leakage and other underground accidents are frequent,resulting in slow drilling speed and long drilling cycle.Therefore,it is necessary to carry out the study of stratigraphic three pressure(the formation pore pressure,collapse pressure,fracture pressure)profile.This paper makes full use of the existing logging data,geological data and drilling data.Based on the theory of rock mechanics and wellbore stability mechanics,this main researchments are as follows:①the lithology analysis of complex strata;②the logging calculation of rock mechanics parameters;③the calculations of stresses and three pressure of formation,and the establishment of the three pressure profile;④the analysis of wellbore stability;⑤programming and processing of multi-Well data.The main findings are as follows:(1)Based on the NCRA method,the lithology of complex strata was analyzed,and the mud content,porosity,permeability and water saturation were calculated.The lithologic volume analysis profile was established,which provided the basis for the calculation of rock mechanics parameters.(2)The shear wave time difference curve of the work area was constructed by using the longitudinal and transverse wave time difference relation in the key well.The calculation model of the rock mechanics parameters and the conversion relation between the dynamic and static rock mechanics parameters was established.So and the longitudinal variation characteristics of the rock mechanics parameters are obtained.(3)According to the characteristics of formation lithology and pore pressure change in the working area,it was found that the influence of the time difference,the resistivity and the density on the effective stress of the formation was large.In this paper,a multivariate nonlinear model based on the effective stress method and ANNBP were used to predict the pore pressure.The results showed that the latter was more accuracy.At the same time,according to the geomechanical characteristics of the structure,the calculation model of the ground stress was preferred.(4)Based on the analysis of the stability of the borehole wall,the calculation model of formation collapse pressure and fracture pressure is established based on the rock failure criterion;At the same time,according to the change characteristics of the three pressure profiles the safety drilling fluid density window was determined.(5)Based on the Forward.NET interpretation platform,the calculation model was programmed to form a "SWPU-9P-SYS" program,which calculates the pressure of three layers of the formation and the safety drilling fluid density window.The program was used to process the logging data of the wells,and the rock mechanics parameters、Insitu stress and stratigraphic three-pressure profile were established of the three wells,Whih the safety drilling fluid density window was given and the stability evaluation of the borehole wall was carried out.Through the above research,a set of methods and techniques of the three pressure profiles for the Shuangyushi tectonic deep gas reservoir is established,Which can be used to determine the safety drilling fluid density window,evaluate the stability of the shaft wall.The results are reasonable and reliable.Which provides a basis for the safe and efficient drilling of the deep gas reservoir.