低压油层防漏堵漏可循环泡沫钻井液及其应用

Circulative Foamed Water Base Drilling Fluids and Their Uses for Controlling and Preventing Circulation Losses in Low Pressure Pay Layers

辽河油田一些开采多年的区块油层亏空,压力低,钻井过程中极易发生井漏。筛选出十二烷基苯磺酸钠为发泡剂,加量0.4%～1.0%;4种聚合物的稳泡效果大小为XC>PAC>HV CMC>80A51,加量0.1%～0.3%。利用所选发泡剂+稳泡剂配制的5种泡沫钻井液,有3种流变性和滤失性较好,密度在0.73～0.79g/cm3,稳定时间>40h,在120℃滚动16h后性能较好,仍能发泡,加入5%NaCl或10%原油对泡沫钻井液粘切影响小,稳定时间>30h;用3种泡沫钻井液对储层岩心进行屏蔽暂堵/返排实验,岩心渗透率恢复率高达90.8%～95.2%;加入泡消剂GY 100或GM801可调整泡沫钻井液密度,直到转化为水基低固相钻井液。在辽河油田锦99块一口定向井三开井段和冷东43块用低密度(<1.14g/cm3)水基钻井液钻进中发生油层漏失的一口调整井使用可循环泡沫钻井液,密度0.65～0.85g/cm3,顺利钻至完钻,未发生井漏,及时发现油气显示,投产后产油量和采油强度均大于邻井。表7。

Circulation losses often occur in drilling in deficient, low pressure pay layers of early exploited reservoirs in Liaohe oil fields. A foaming agent, sodium dodecyl benzene sulfonate, is chosen with dosage being of 0.4～1.0% and 4 polymers are arranged according to their foam stabilizing power in order XC>PAC>HV-CMC>80A51 with dosage being of 0.1—0.3%. Five foamed water base drilling fluids (FWBDFs) are formulated and prepared with the foaming agent and the foam stabilizer chosen and three of these have satisfactory rheologic and filtration behavior, density ranged 0.73—0.79 g/cm^3 and foam stabilization time >40 hrs; good properties and foaming power are maintained after rolling at 120℃ in 16 hrs; introducing 5% NaCl or 10% crude oil does not affect the viscosity/yield behavior of one of these FWBDFs significantly and foam stabilization time is >30 hrs; in screening/temporarily plugging/inverse flooding experiments with the FWBDFs the recovery of core permeability is as high as 90.8—95.2%; the density of the FWBDFs can be adjusted with the help of a defoamer, GY-100 or GM801, and, in extreme cases, an FWBDF can be converted to a water base low solid phase drilling fluid. In an adjustment well in reservoir Lengdong-99, Liaohe, where a loss of circulation occurred in pay layers while drilling performed with a water base fluid of low density <1.44 g/cm^3, and in a directional well in reservoir Jing-99, Liaohe, applying FWBDFs of density 0.65—0.85 g/cm^3 leads to successful completion of the drilling jobs without any circulation loss and with the oil/gas show detected in time; the productivity and the production rate of the two wells are higher than that of the neighbor wells.