东溪构造南段低渗透储层分层酸化效果分析

RESULT ANALYSIS ON LAYERED ACIDIZATION OF LOW-PERMEABILITY GAS RESERVOIR AT THE SOUTHERN SECTION OF DONGXI STRUCTURE

东溪气田在纵向上有多套产层,平面上存在北段中渗区、中段高渗区、南段低渗区。北段中渗区、中段高渗区大部分气井进入开采末期,而南段低渗区由于储层渗透性较差、产量低、采气速度慢、采出程度低,仍具有较大的勘探开发潜力。为此,针对东溪构造南段低孔、低渗、低压、多产层的地质特点,在综合分析钻井、完井、射孔、酸化工艺和对东浅1、2井、东4-1井认识的基础上,东浅3、4井采用了定向钻进,使产层暴露井段长,完井方法采用139.7mm套管射孔完成,并将3个主要产层全部打开,经对嘉五1、嘉四3层和嘉三段实施分层泡沫酸酸化,测试产量分别为7.6×104m3/d、5.92×104m3/d,较东浅1、2井和东4-1井产量有显著的提高,取得了东溪构造南段低渗透储层的产量突破,达到了提高单井产能的目的。

In the Dongxi Gasfield, there distributed vertically multiple sets of pay zones, while areally medium-seepage area in the north, high-seepage area in the middle, and low-seepage in the south. Most of gas wells both in the north and middle have come to the end of production, but gas wells in the south have a great potential of exploration and production because the production rate and speed are extremely low due to low-permeability gas reservoirs there. Aiming at the southern section of Dongxi structure characterized by low-porosity, low-permeability, low pressure and multiple pay zones, this study analyzed completely on full knowledge of the wells Dongqian-1,2, 3, and Dong 4-1, and the proper technologies to be taken here such as drilling, completion, perforating, and acidization. After adopting such successful technologies on the wells Dongqian-3, 4, this study concluded obvious good results as follows: (1) directional drilling increased the naked well section of pay zones to improve productivity of the wells; (2) foam acidization had good advantages of satisfactory flowback, long effective acceptance range and easy turnabout, adapt for the recovery of those reservoirs in the south; (3) much better acidization effects were obtained by well completion (139.7 mm casing for perforating) and layered foam acidizing (T1j51, T1j43, T1j3). This paper concludes that some technologies adopted successfully in the southern section of Dongxi Structure should be taken as references for further drilling, completion, and recovering those similar reservoirs.