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水平井分段压裂是致密砂岩气藏开发的有效手段,数值模拟表明,缩短缝间距,可以大幅度降低油气流动压差,从而提高单井产量。随着储层品质变差,川西沙溪庙组气藏常规分段(缝间距80~100m)效果变差,采出程度低。在地层压力不同的区域,采用自主研制的不动管柱不限级数滑套分段工具,试验了水平井细分段、拟体积压裂改造。不动管柱分段数最多达到20段,平均段间距为46.3m,平均入地液量为2 775.6m~3。压后对比表明,高压气藏压裂效果好,生产相同时间,较常规分段井累计产量高,稳产好;但常压气藏压后压力降落快,返排困难,压后效果差。对此,结合岩心伤害实验分析了常压气藏压后效果差的原因,认为长时间、大液量施工,对储层渗透率伤害大,同时常压储层地层能量低,滤失到储层的液体难以返出,是导致该类气藏细分段、拟体积压裂返排困难,压后效果差的主要原因。建议致密砂岩常压气藏,不采用水平井细分段、大规模拟体积压裂改造;高压气藏可以推广应用。研究为类似气藏开发提供了借鉴。
Horizontal well fracturing is an effective method for the development of tight sandstone gas reservoirs. Numerical simulation shows that shortening the gap between the fractures can greatly reduce the differential pressure of oil and gas flow so as to increase single well productivity. With the deterioration of the reservoir quality, the gas accumulation in the Shaximiao Formation in the western Sichuan Province has become less effective due to the conventional subsection (seam spacing 80-100m). In the areas with different formation pressures, the self-developed immobile series of infinite series slide block tools were used to test the subdivision of horizontal wells and to simulate the volumetric fracturing. The number of immobile columns reached a maximum of 20 sections, with an average interval of 46.3 m and an average volume of 2 775.6 m ~ 3. The comparisons show that the fracturing effect of high-pressure gas reservoirs is good and the production time is the same. Compared with the conventional sectional wells, the cumulative yield is high and the stable output is good. However, the pressure of normal pressure reservoirs lacks rapidly after pressure, and the backflow is difficult and the pressure effect is poor. In this regard, combined with the core damage experiment analysis of the atmospheric pressure after the pressure effect of poor, that a long time, a large amount of liquid construction, the permeability of the reservoir damage, while low pressure reservoir pressure, reservoir to the reservoir Layer of liquid is difficult to return, is leading to subdivision of such gas reservoirs, the proposed volume of fracturing back row difficulties, the main reason for the poor pressure effect. It is suggested that tight sandstone atmospheric reservoirs should be replaced by large-scale pseudo-volume fracturing instead of using horizontal wells and high-pressure gas reservoirs can be popularized and applied. Research provides a reference for the development of similar gas reservoirs.