Abstract: he carbonate reservoir has tight lithology and is operated at high temperature in S block. In order to improve the oil recovery, it is necessary to carry on the acid fracturing treatment to the target reservoir. According to the characteristics of the target reservoir, the acid fluid for acid fracturing was optimized and evaluated. Through the porosity and permeability experiment, the porosity of S block was 0.1%~2.0%, and the permeability was below 0.01 mD, which belonged to ultra⁃low permeability reservoir. According to the uniaxial compression test, the compressive strength of the reservoir was high, ranging from 40 to 70 MPa. X⁃ray diffraction showed that dolomite and calcite were the main minerals in the reservoir ( 80%~90% in total), with a small amount of quartz and clay (mass fraction was about 10%). The main acid was 20% hydrochloric acid, the thickener was 0.3% xanthan gum, and the dissolution rate of rock powder was about 90% when hydrochloric acid acted alone, and the main acid solution was hydrochloric acid. Taking into account that the reservoir lithology of carbonate rock in S block was dense and the formation temperature was 100~140 ℃, the viscosity of modified xanthan gum was about 10 mPa·s at 140 ℃. The modified xanthan gum was selected as high temperature resistant thickener.

Key words: Carbonate rock, Tight reservoir, Acid fracturing with high temperature, Acid liquor

摘要： S区块碳酸盐岩储层岩性致密，施工温度较高，为了提高采收率，需要对目标储层进行酸压处理。针对目标储层的特点，对酸压所需酸液进行优选评价。通过孔渗实验，测得S区块储层孔隙度为0.1%~2.0%，渗透率在0.01 mD以下，属于超低渗储层；通过单轴压缩实验测得储层抗压强度较高，在40~70 MPa；通过X射线衍射测得储层矿物成分以白云岩和方解石为主，两者质量分数可达80%~90%，少量石英和黏土（质量分数在10%左右）。确定主体酸为质量分数20%盐酸，稠化剂为质量分数0.3%黄原胶，进行了岩粉溶蚀实验，盐酸单独作用时溶蚀率可达90%左右，优选主体酸液为盐酸；考虑到S区块碳酸盐岩储层岩性致密，地层温度在100~140 ℃，通过高温流变性实验，测得140 ℃时改性黄原胶黏度约为10 mPa·s，选择改性黄原胶作为耐高温的稠化剂。

关键词: 碳酸盐岩, 致密储层, 高温酸压, 酸液配方