Study On Technology Of Low Damage High Density Non - Solid Phase Filling Fluid

As the exploration and development of oil and gas in East China Sea Oil And Gas Field constantly extend to the deeper reservoirs,some of which have low porosity and permeability. The problem of high temperature and high pressure becomes more and more prominent. Thus there has been a must to develop high density fluid without solid for well testing fluid and well-killing fluid technology which is resistant to higher temperature and is less harmful to the reservoir. The functions of confirming safety under high temperature,testing effectively and well-killing can be achieved.This article introduces characteristics of tectonic and sedimentary in PingBei II stage at first. Additionally,with analyzing the characteristics of those reservoirs, which include lithology,reservoir space types,physical indicators,pore structure and sensitivities of clay minerals,the potential factors of formation damage in this stage can be indicated as follows: neither water nor acid sensitivity is strong, especially in acidification operation. The heterogeneity of those reservoirs are relatively serious,of which the structure of pore characterized by small pore diameter and with mainly micro pore and throat. Thus these characters are vulnerable to damage with particles (illite) dispersion and transportation. As nonuniform distribution of gas and water in micro scale in the pore structure which brings the deviant flow of gas and water,there could be water lock damage and Ja min effect.Because both inorganic and organic salt solubility in the freshwater or seawater are certain,the density of the ordinary solid free test fluid and well killing fluid is generally not very high,thus leading to great difficulties in the choice of well testing fluid and well-killing fluid for high temperature and high pressure wells. A solution of this problem is to use the solubilization technology to improve the solubility of the inorganic or organic salt,so that well testing fluid and well killing fluid may meet the needs. However,in general,after the solubility of salt reaching a certain height,it can make unstable problems. Therefore the cosolvent technology overcomes the problems of the stability of the test fluid,causing that it not only has good thermal stability,but also has very good stability in the process of transportation and pumping into the well,which ensures consistency of the density in various conditions. The solubilization and cosolvent technology are simply introduced in this article. And some evaluation experiments have been done which are involving the damage to reservoir caused by currently used high temperature and high pressure of well drilling fluid and completion fluid without solid in East China Sea Oil And Gas Field, which give reference and guidance to the research and development of well killing fluid. Eventually based on WJZ-1solid free weighting agent,HZR-1solubilizer,NTA-2salt crystallization inhibitor and HCY-1corrosion inhibitor,the article successfully developed the HWJZ well killing fluid system without solid,its ability to resist temperature can reach more than170℃,and the highest density can reach1.80g/cm3.Based on Pingbei stage Ⅱ lithologic reservoir physical property characteristics of block,through a large number of experiments in the laboratory,the results prove that the HWJZ well killing fluid system without solid can resist high temperature,has non-toxic and very good protection of the reservoir.Site operation results show that the low damage and high density well killing fluid without solid under the condition of high temperature has stable performance,and ensure the smooth progress of the well-killing operation.