Research On Formation Water Production And Bionic Processing Technology In Gas Drilling

Gas drilling has become an important technology of oil and gas exploration and development because of the special advantages like higher penetration rates, avoidance of lost circulation, handing complicated accidents of borehole and effective detection and protection of oil and gas reservoir. But its application may be restricted seriously because of annular plugging, balling-up sticking, wellbore instability and other complicated accidents caused by clay hydration and swelling when drilling through the water-bearing formations. So, the research on formation water production and bionic processing technology in gas drilling has been studied and achievements are as follows:(1) Analyze the plastic limit, liquid limit, plastic index and liquid index of shale powder in different conditions and the adhesion characteristics in plastic state and flow state. The clay content and types in shales and the aqueous solution characteristics blended with shales determine the distribution of shale power plastic index and liquid index and also effect the adhesion characteristics in different liquid-solid ratio. Study on the water invasion during gas drilling with formation water production, analyzing the water invasion characteristics in shale formation and the important role of capillary force in water invasion. The effects of clay hydration and swelling on shale rock mechanics parameters have been studied through the analysis of shale rock mechanics parameters. And based on the filed cases, the effects of formation water production or not on the wellbore stability in gas drilling have been compared for the same formation.(2) Based on the bionics principle, research on bionic processing technology in shale formation has been carried out and the technological process to realize the hydrophobic treatment on shale surface also has been proposed. Through the optimization and performance evaluation of different treatment agents, the bionic treatment fluid formulation has been developed with4%SMS+0.4%KH550+1%JHCY. Related performance evaluation shows that: the wettability change of shale surface from hydrophilic to hydrophobic can be realized to hinder the formation water invasion using the low surface energy characteristics and self-polymerization effect of organic silicon agents to form nano coarse structure with "lotus effect"; The bionic hydrophobic surface formed in shale surface has certain abrasion resistance and stability characteristics; And before forming hydrophobic surface protective layer, the bionic treatment fluid is not good with the stability of shale formation.(3) Through analyzing the characteristics of foam fluid, the foam fluid is low density fluid, can uniformly absorb on the shale surface and has convenient foam drainage speed control by adjusting fliud viscosity, so the biomimetic treatment fluid can be in the form of foam fluid to contact with the shale surface. Through the optimization and performance evaluation of foaming agents, stabilizing agents and shale inhibitors, the highly inhibitive stable foam fluid formulation has been developed with0.8%FPH+0.1%XC+0.5%PVA+3%DA-1. Related performance evaluation shows that the foamability can be easily influenced by solution pH value and the great foamability appears in alkaline condition. And the foam fluid has permanent and great shale inhibition to stabilize the borehole wall in the bionic processing.(4)Through the combination of the biomimetic treatment fluid and the highly inhibitive stable foam fluid, the final bionic foam processing fluid formula has been developed with0.8%FPH+0.1%XC+0.5%PVA+3%DA-1+4%SMS+0.4%KH550+1%JHCY. The comprehe-nsive performance evaluation shows that:the bionic foam processing fluid has great foaming properties, acid-base foam circulation characteristics, great temperature tolerance and contamination resistance, and highly and persistently shale inhibition. When the hydrophobic surface protective layer formed, it can effectively prevent the free water invasion, thus prevent clay minerals hydration and maintain the stability of shale formation, but the treatment is suitable for the formation where the formation temperature is below80℃.