基于新型增黏剂的低密度无固相抗高温钻井液体系

在分子设计的基础上,以AMPS、N-乙烯基己内酰胺、二乙烯苯为共聚单体,研制出了新型抗高温聚合物增黏剂(SDKP)。SDKP的分子量不高,但当其浓度达到临界缔合浓度时,分子中的疏水链段以及分子微交联结构中的疏水苯基之间可产生疏水缔合作用,形成较大的动态物理交联网络,从而起到增黏作用。采用Haake RS6000流变仪进行的评价结果表明,SDKP具有优良的高温增黏特性,抗温达165℃。通过对抗氧化剂、降滤失剂、润滑剂和抑制剂的优选,研制出了一套密度为1.02 g/cm3、耐温能力达190℃的低密度无固相抗高温钻井液(WGX)体系。评价结果表明:WGX体系在170℃、5.5 MPa下的表观黏度和塑性黏度分别大于30 m Pa s和17 m Pa s,高温携岩能力较强;岩心渗透率恢复率大于90%,油层保护性能好;抗Na Cl、劣质土污染能力分别达5%和10%,具有一定的抗污染能力;膨胀率仅为7.22%,泥页岩回收率高达89.33%,防塌抑制性好;极压润滑系数仅为0.085,润滑性能好。

Development and Evaluation of Low Density Solids-free High Temperature Drilling Fluid

Organic salts are presently used to improve the high temperature stability of solids-free drilling fluids, which have higher density because of the presence of organic salts. Higher density plays a negative role in the protection of deep high temperature lowpressure reservoirs. A solids-free high temperature drilling fluid, WGX, was recently formulated with a newly developed viscosifier SDKP, and a series of selected additives such as antioxidant, filter loss reducer, lubricant and inhibitive agent. WGX had a density of 1.02 g/cm3 and remained stable at 190℃. Performance evaluation showed that WGX had good high temperature rheology and good carrying capacity at high temperature. Permeability test gave a percent permeability recovery of greater than 90%. The rheology of WGX remained satisfactory even when contaminated with 5% NaCl or 10% clays. Percent rate of swelling of cores tested with WGX was only 7.22%, and hot rolling test showed a percent recovery of shale samples of 89.33%. WGX tested on an extreme lubricity tester showed that the extreme frictional coefficient was only 0.085.