南海低渗透储层支撑剂导流能力试验研究

Experimental Study of Proppant Conductivity in Low Permeability Reservoirs in the South China Sea

针对南海低渗透储层油气采出程度低、压裂难以形成高导流能力人工裂缝的问题,通过室内试验分析了储层黏土矿物含量、不同粒径支撑剂组合方式和破胶液黏度对人工裂缝导流能力的影响。在试验条件下,储层黏土矿物含量从15%增至50%,20/40目支撑剂导流能力的降低率从13.84%增至31.34%;20/40目、30/50目和40/70目陶粒以3∶1∶1的比例铺置时最优,该组合最终导流能力为116.7 D·cm;破胶液黏度为1 mPa·s时,支撑剂导流能力最高。试验结果表明:随着黏土矿物含量增大,支撑剂导流能力逐渐降低;支撑剂的破碎主要由于支撑剂颗粒相互挤压而非与储层的相互作用;不同粒径支撑剂组合铺置时,大粒径支撑剂占比越大,导流能力越高;随着闭合压力升高,小粒径支撑剂破碎所造成的渗透率下降是造成导流能力降低的主要原因;破胶液黏度越低,支撑剂导流能力越高。研究结果可为南海低渗透油气藏压裂选层和优化压裂方案提供依据。

The degree of reserve recovery in low permeability reservoirs in the South China Sea is low,and high-conductivity fractures are difficult to create from hydraulic fracturing.Laboratory studies were conducted to analyze the impact of clay mineral content,combination mode of proppants with different grain sizes,and gel-breaking liquid viscosity on fracture conductivity.Studies showed that the conductivity reduction rate of the 20/40 mesh proppant went up from 13.84%to 31.34%when clay mineral content increased from 15%to 50%under testing conditions.The optimal ratio for ceramsites sized in 20/40 mesh,30/50 mesh and 40/70 mesh was 3∶1∶1,with a final conductivity of 116.7 D·cm.The maximum proppant conductivity achieved at a gel-breaking liquid viscosity of 1 mPa·s.According to the experimental results,with the increase in clay mineral content,proppant conductivity would decrease.Proppant crushing is mainly caused by compression among proppant particles rather than the interaction of the proppant with the reservoir.A larger proportion of proppant with a larger grain size results in higher conductivity when the proppant is combined with different grain sizes.Permeability decreases from proppant crushing with a small grain size is the main reason for conductivity loss as closure pressure increase.A lower gel-breaking liquid viscosity indicates a higher proppant conductivity.The research outcomes can provide a reference for stimulation candidates selection and fracturing scheme optimization of low permeability reservoirs in the South China Sea.