柴达木盆地英西地区缝洞型碳酸盐岩储层体积改造技术研究与应用

Research and application of volume fracturing technology for fractured carbonate tight formation in Yingxi area,Qaidam Basin

柴达木盆地英西地区缝洞型碳酸盐储层碳酸盐岩含量为40%～50%、埋深在3 600～4 700m之间、地应力梯度为0.020MPa/m,裂缝发育密度为2～8条/m、基质渗透率为(0.01～0.9)×10-3!m2,以往酸化及酸压后单井产量低、递减快、有效期短、累计产量小。借鉴体积改造理念,通过增大改造规模增加水力裂缝长度沟通油气富集区,采用大排量、高比例滑溜水、复合粒径支撑剂施工提高裂缝复杂程度,保证压后效果。2017年在英西碳酸盐储层进行体积压裂改造4口井(水平井1口),压后效果显著:直井压后初产是2016年施工井的1.8倍,水平压后初产是直井的21倍,其中SH1井压后日产油为395m3、天然气为5 796m3。研究成果为其他裂缝型碳酸盐岩致密储层改造提供了经验。

The fractured carbonate reservoirs in the Yingxi area of Qaidam Basin have characteristic of carbonate content of 40%-50% ,burial depth of 3 600-4 700m,stress gradient of 0.020MPa/m,natural fracture density of 2-8/m and matrix permeability of （0.01-0.9）×10-3μm2.After the traditional acidizing and acidfracturing method, we are still facing problems such as low oil recovery, fast decrease, short production pe riod and low cumulative output.Drawing on the concept of volume fracturing,fractures length and connected oil gas enrichment area increased by the increase of fracturing scale. What＇s more, large scale pump, highslick water proportion and combined proppant methods were used to increase the fracture complexity and the output effect.In 2017,4 wells （including a horizontal well） were constructed in this area and the results showed that the primary production of vertical wells increased 1.8 times and the output of the horizontal well was 21 times than vertical wells,e.g. ,oil and gas rate of Well SH1 is 395m3/dand 5 796m3/dafter volume fracturing.Study of this paper can provide experience for other fractured carbonate tight reser voirs.