火山岩气藏压裂难点诊断及处理控制

Diagnosis and treatment control for the complexities of hydraulic fracturing in volcanic gas reservoirs

火山岩天然气藏多数须压裂增产才具工业开采价值,但火山岩中的孔隙、溶孔及天然裂缝个性差异大,国内外均没有成熟的压裂工艺,增产投资高、风险大、效果差。如何准确诊断压裂难点和研究实施有针对性的处理措施,已成为火山岩气藏勘探开发取得突破的关键。在研究火山岩复杂结构对压裂G函数影响的基础上,归纳出常规滤失型、低滤失型、微裂缝发育型、微裂缝极发育型和高裂缝型5种典型G函数特征,形成了保证人造主裂缝形成工艺、处理近井复杂摩阻高工艺、压裂施工参数优化工艺、选择合适的加砂泵注程序等针对性的控制处理措施。经过在松辽盆地北部徐家围子气田超过100口井的应用,压裂成功率、施工规模及单井增产效果均取得突破,有效地提高了火山岩气藏压裂成功率和效果。

Volcanic gas reservoirs are widely distributed in the northern Songliao Basin,but most of them need fracture treatment before industrial exploitation.In addition,volcanic pores,holes and natural fractures show high heterogeneity to a high degree.However at present there is no mature fracturing technology both at home and abroad,as a result the frac-treatment success ratio is very low.Therefore to diagnose the fracturing complexities,to study the treating countermeasures,and to put them into practice have become the key factors in the exploration and exploitation of volcanic gas reservoirs.This paper hereby studied the impacts of complex structures in reservoir space on the G-function and generalized five kinds of representative G-function characteristics,including the types of conventional filtration,low filtration,microfracture development,microfracture extreme development and high fractured.Accordingly,four kinds of treating measures have also been presented here as follows:the process to ensure the formation of an artificial main fracture,the technology in dealing with high friction in the complex near-wellbore,the technology in fracturing process parameter optimization,and the technology in selecting the proper program of sand adding and pumping.Successful application of these techniques in over 100 wells with the frac-treatment success rate increased from 37.5-93% in Daqing Xujiaweizi gas field proves that these techniques help make a breakthrough in proppant adding and post-frac production in volcanic gas reservoirs.