致密储集层小型压裂压降分析方法的改进与应用

Improvement and Application of Pressure Drop Analysis Method for Mini-Fracturing in Tight Reservoirs

通过分析小型压裂压降曲线可以了解储集层压裂特征,获取储集层物性参数,但常用的致密储集层小型压裂压降分析方法存在G函数表达式选用不合理,天然裂缝开启条件下的储集层滤失未量化,储集层物性参数求解方法现场实效性弱等问题。为此,首先计算裂缝延伸指数并给出了合理选用G函数表达式的方法,然后对天然裂缝开启条件下的储集层滤失系数表达式进行了修正,进而提出了裂缝闭合后线性流压降分析方法以快速获取储集层物性参数。通过实例应用,验证了改进后的方法在致密储集层压裂分析中的适用性及可靠性。

Fracturing characteristics and physical parameters of reservoirs can be acquired by analyzing pressure drop curves during minifracturing. But there are some defects of the commonly used methods of pressure drop analysis due to its unreasonable G function expression, unquantified filtration coefficient under the condition of natural fissure opening and weak effectiveness of the method for reservoir physical parameter calculation. Therefore, the reasonable selection method of G function expression on the basis of calculating fracture extension index is given at first. Then the method to calculate filtration coefficient with open natural fissures is modified and a method to analyze linear pressure drop after the closure of fissures is proposed to obtain reservoir physical parameters rapidly. The actual application results can verify the applicability and reliability of the improved method in tight reservoir fracturing analysis.