强非均质性碳酸盐岩气藏水平井精准分段酸压技术——以四川盆地中部高石梯—磨溪震旦系灯四段气藏为例

Specified staged acid fracturing of horizontal well for strong-heterogeneity carbonate gas reservoirs:A case study on the gas reservoir of the fourth Member of Upper Sinian Dengying Formation in Gaoshiti-Moxi area of the central Sichuan Basin

四川盆地中部高石梯—磨溪地区(以下简称高磨地区)上震旦统灯影组四段(以下简称灯四段)碳酸盐岩气藏的储层具有埋藏深、地层温度高、孔隙度低、渗透率低且非均质性强等特征。为了实现该气藏储量的有效动用、提升气藏的开发效益,综合考虑钻录井参数、测井解释参数及井型特征参数,定义储层改造系数,开展储层量化评价;综合考虑储层改造系数、地应力和井眼条件,形成精细分段方法,并且针对不同类型的储层,形成差异化酸压改造工艺;在此基础上,形成了强非均质性碳酸盐岩储层水平井精准分段酸压技术,并在现场进行了应用。研究结果表明:①储层改造系数(y)能够较准确地评价储层特征,y≥1.0为优质储层,0.5≤y<1.0为中等储层,y<0.5为低品质储层;②形成了综合考虑储层改造系数、地应力和井眼条件影响的酸压精细分段方法,对不同类型储层段实施有针对性的改造措施,充分发挥长水平井段各改造段的资源潜力,提高强非均质性储层中天然气储量的动用率;③不同类型的储层所适用的酸压工艺也不相同——对于优质储层宜采用胶凝酸或转向酸酸压工艺,对于中等储层宜采用自生酸前置液酸压工艺,对于低品质储层宜采用自生酸前置液+胶凝酸2~3级交替注入酸压工艺;④对高磨地区灯四段气藏台缘带建产区69口井实施了精准分段酸压,井均天然气无阻流量为127.6×10^(4) m^(3)/d,比气藏开发初期提高了46.5%。结论认为,该研究成果的增产改造效果显著、单井产气量得以大幅度提升,有效地支撑了该区灯四段气藏的高效开发。

The reservoir of the carbonate gas reservoir of the fourth Member of Upper Sinian Dengying Formation(hereinafter referred as"Deng 4 Member")in the Gaoshiti-Moxi area of the central Sichuan Basin is characterized by great burial depth,high reservoir temperature,low porosity,low permeability and strong heterogeneity.In order to effectively produce the reserves of this gas reservoir and improve its development benefits,this paper defines the reservoir stimulation factor by comprehensively considering the drilling,mud logging,logging interpretation and well type characteristic parameters,to carry out quantitative reservoir evaluation.Then,the refined segmentation method was developed by fully considering the reservoir stimulation factor,in-situ stress and borehole condition.In addition,the differential acid fracturing technology was prepared for different types of reservoirs.On this basis,the specified staged acid fracturing technology of horizontal well for strong-heterogeneity carbonate reservoirs was developed and then applied in the field.And the following research results were obtained.First,the reservoir stimulation factor(y)can be used to accurately evaluate the reservoir characteristics.The high quality reservoir has y≥1.0,the moderate reservoir has 0.5≤y<1.0,and the low quality reservoir has y<0.5.Second,the specified staged acid fracturing technology considering the influence of reservoir stimulation factor,in-situ stresses and borehole condition comprehensively is formed.Stimulation measures are applied specifically in different types of reservoir intervals to give full play to the resource potential in each stimulation segment of a long horizontal section,so as to improve the production rate of natural gas reserves in strong-heterogeneity reservoirs.Third,the acid fracturing technology suitable for different types of reservoirs is also different.It is recommended to adopt acid fracturing with gelled acid or diverting acid in high quality reservoirs,acid fracturing with self-generating acid prepad in moderate reservoirs,and acid fracturing with 2-3 stages alternate injection of self-generating acid prepad and gelled acid in low quality reservoirs.Fourth,69 wells in the productivity construction area of the platform margin of Deng 4 Member gas reservoir in Gaoshiti-Moxi area are stimulated with specified staged acid fracturing.The average absolute open flow is 127.6×10^(4) m^(3)/d,which is 46.5% higher than that in the early stage of gas reservoir development.In conclusion,the research results provide remarkable stimulation effects,increase the single well gas production greatly and effectively support the efficient development of Deng 4 Member gas reservoir in the Gaoshiti-Moxi area.