Study On Water-based Drilling Fluid For Reservoir Protection In Ultra-low Permeability Gas Reservoirs In Keshen Block

As the development of unconventional oil and gas fields, HTHP tight gas fields now have entered the phase of rapid development. According to the reservoir characteristics of high temperature and high pressure, corresponding study should be used for reservoir drilling fluid, in order to satisfy the demands of high temperature and high pressure reservoir normal drilling. Because of the tight gas reservoir pore throat is extremely small, and the development of cracks, dense gas reservoir protection has become the current one of the great difficulties in high temperature and high pressure gas reservoir.we should take methods for effective protection measures.This thesis aimed at the problems of present polysulfide drilling fluid performance of Keshen is poor, from research potential damage factors of reservoir and the reservoir damage mechanism, it is concluded that the deep block reservoir protection emphasis and difficulty; through a lot of laboratory experimental research and literature research, the author selects some agents for HTHP water-base drilling fluid, such as package agent, fall lost agent, inhibitor, viscosity agent, lubricant treatment agent, etc,and compounds with potassium calcium base-polysulfide water-based drilling fluid system. Authors do some experiments to exam the system performance. Potassium calcium base-polysulfide formula for water-based drilling fluid system is 2.5%?3% bentonite+0.1%Na2CO3+0.02%?0.05%FA367+ 0.5%?0.8%PAC-LV+0.8%?1%PAEM+4%-6%SMP-?+3%?5%M-SMC+ 2%?4%RSTF+1%?3%RH220+1%?2%FT-1+0.1%?0.3%XY27+7%KCl+ 0.3%?0.5%CaO+barite. For deep block reservoir with cracks, micro cracks as the main object of protection, adopted Mosaic of temporary plugging reservoir protectionExperiments show that this paper developed by potassium calcium base-polysulfide water-based drilling fluid system not only has good rheological property, filter loss of wall building, ability to resist pollution. By adding reservoir protective agent, this system also has good capability of reservoir protection. After joining reservoir protectant agents,water-base drilling fluid still meets normal drilling. The drilling fluid technology research not only has strong theoretical significance, but also has important practical value.