全缝长酸蚀填砂裂缝导流能力评价方法

Evaluation Method for the Conductivity of Full-Length Sand-Packed Acid-Etched Fractures

为了准确评价加砂复合酸压时支撑剂对酸蚀裂缝导流能力的影响,从而确定加砂时机,提出了全缝长酸蚀填砂裂缝导流能力评价方法。以顺北油田奥陶系储层为例,采用酸压数值模拟确定了储层条件下裂缝不同位置的温度、酸液质量分数和铺砂浓度等关键试验条件,测试了酸蚀填砂裂缝不同位置的导流能力。试验结果表明:裂缝中不同位置的反应温度对酸刻蚀效果的影响大于酸液质量分数,导致裂缝中部酸刻蚀效果最好,缝尾次之,缝口较差;闭合应力大于60 MPa时,酸蚀裂缝的中部和远端填砂可显著提升导流能力。S3井采用该方法确定酸压中期加砂提升裂缝中、远端的导流能力,改造后稳定日产油量较邻井提高了40.0%,稳产时间延长了57.8%。全缝长酸蚀填砂裂缝导流能力评价方法,克服了常规试验方法难以评价储层条件下百米级裂缝导流能力的局限,为复合酸压加砂时机的确定提供了新的手段。

In order to evaluate the influence of proppant on the conductivity of acid-etched fractures during the composite acid fracturing with sand and determine the timing of adding sand,an evaluation method for the conductivity of sand-packed acid-etched fractures at full-length scale was proposed.The Ordovician reservoir in Shunbei Oilfield was taken as an example.Firstly,acid fracturing numerical simulation was used to determine the key test conditions such as temperature,mass fraction of acid solution,and sand concentration at different positions of fractures under reservoir conditions,and then the conductivity of sand-packed acid-etched fractures at different positions was tested.The results showed that the impact of reaction temperature at different positions of the fractures on the acid-etching effect was greater than that of the mass fraction of acid solution,which led to the best acid-etching effect in the middle of the fractures,followed by the fracture tail,and the fracture inlet was the worst.When the closure stress was greater than 60 MPa,sand filling in the middle and tail of the acid-etched fractures could significantly improve the conductivity.This method was applied in Well S3 to determine the sand addition during the metaphase of acid fracturing,so as to improve the conductivity in the middle and tail of the fractures.After the stimulation,the stable daily oil production was increased by 40%compared with the adjacent wells,and the stable production time was extended by 57.8%.The evaluation method for the conductivity of full-length sand-packed acid-etched fractures overcomes the difficulty to evaluate the conductivity of fractures with the order of 100 meters under reservoir conditions which is a limitation for conventional tests and provides a new method for determining the timing of adding sand in composite acid-fracturing.