海上油田高温解堵液体系

海上油田X-1井砂岩储层具有高温、异常高压和低渗等特征，且储层岩样溶蚀孔发育，含有一定的粒间缝被黏土矿物充填，黏土矿物较多，易造成水敏、速敏。针对上述问题研制出一种高温低渗敏感性储层解堵液体系。实验表明，在170℃的条件下，解堵液体系对钢片的平均腐蚀速率为62.880 g/m2·h，达到行业一级标准，且该体系具有较低的表面张力，鲜酸和残酸表面张力均低于24.0 mN/m。解堵液体系有较好的稳定铁离子能力，稳定铁量高达263 mg/mL。解堵液体系具有较好的防膨效果，终膨胀率降低值为32.19%，能有效控制黏土膨胀，抑制水敏伤害。岩心中注入解堵液体系后，渗透率呈明显的上升趋势，由于该体系对黏土矿物和基质的溶蚀率均较大，且不宜引起出砂堵塞孔喉，渗透率增加倍比约为3.5倍，是较为理想的适用于高温低渗储层的解堵液体系。现场应用表明，解堵液基本解除井筒附近堵塞，对比酸化前后日产气量，本次酸化对该井起到了很好的解堵效果。 

A High Temperature Block Removal Fluid for Offshore Application

The sandstone reservoir penetrated by the well X-1 in an offshore oilfield has the characteristics of high temperature, abnormally high pressure and low permeability. Dissolution pores are developed in the reservoir rocks. Intergranular fractures in the reservoir rocks are full of various kinds of clays which are easy to cause water sensitivity and flow velocity sensitivity. To solve these problems, a blocking removal fluid was developed for use in the high temperature low permeability sensitive reservoirs. Laboratory experimental results showed that at 170℃, the average corrosion rate of the steel strip in the blocking removal fluid is 62.880 g/cm2·h, meeting the first-grade standard of the industry. The blocking removal fluid has lower surface tension, the surface tensions of the fresh acid and residue acid are all less than 24.0 mN/m. The blocking removal fluid has good ferric ion stability, it can stabilize 263 mg/mL of ferric ions in a system. The blocking removal fluid has good clay swelling inhibition capacity, the final rate of swelling of a sample can be controlled below 32.19%, this is helpful to effectively inhibit water sensitivity impairment to the reservoir. After injecting the blocking removal fluid into a core, the permeability of the core was apparently increasing. The blocking removal fluid is ideal for removing blocks existed in high temperature low permeability reservoirs because the dissolution rates of the blocking removal fluid to clay minerals and the matrix of the rock are high, the blocking removal fluid do not cause pore throats to be blocked by the produced sands, and the permeability of the core can be increased by 3.5 times. Field application showed that the blocking removal fluid removed almost all the blockage near the wellbore. Comparison of the daily gas production rates before and after acidification of the reservoir showed that the acidizing job has done very well in removing the blockage in the reservoir formation.