绳结暂堵塞性能研究及现场应用

Research on Temporary Plugging Performance of Knot and Its Field Application

非常规油气藏物性致密,段内非均质性强,笼统压裂容易使裂缝沿优势簇延伸,导致压裂改造不均匀、压后效果不理想。暂堵是提高各簇改造均匀程度的有效方法,但常规暂堵球多为固定球形,不具备变形特点,且承压强度低、溶解性差,难以有效封堵不规则优势孔眼,导致压裂改造效果不佳。因此,本文研究了一种韧性绳结暂堵塞,其特殊的绳体+尾翼结构具有可变形的特点,能有效暂堵不规则孔眼,既不会穿过孔眼,也能避免因压差降低而造成脱落。室内对其降解、抗拉、承压性能进行了评价,结果表明:绳结暂堵塞抗拉强度大于110MPa,承压能力可达75MPa;其降解性能仅受温度控制,在40~175℃的温度下,绳结暂堵塞在模拟地层水中5h内无明显变化,72h内降解率能够达到100%,降解产物为二氧化碳和水。在现场应用6井次,成功率100%,其中B-3井应用结果表明,各段投入绳结暂堵塞后施工压力增幅较大,平均增量为5.4MPa,现场监测结果显示暂堵后裂缝体积明显提升,证明了绳结暂堵塞的有效性。

Due to the tight physical properties of unconventional oil and gas reservoirs and the strong heterogeneity in intervals,general fracturing is easy to make fractures extend along the dominant clusters,resulting in uneven fracturing and unsatisfactory post-fracturing effect.Temporary plugging is an effective method to improve the uniformity of each cluster,but the conventional temporary plugging balls are mostly fixed spherical,and it is difficult to effectively plug irregular dominant holes,resulting in poor fracturing effect because of no deformation characteristics,low bearing strength and poor solubility.Therefore,a tough knot for temporary plugging is researched in this paper.Its special rope+tail structure has the characteristics of deformability,which can effectively plug irregular holes temporarily without passing through the holes and avoid falling off due to pressure difference reduction.The degradation,tensile strength and bearing capacity of the rope were evaluated indoors.The results show that the tensile strength of the knots is greater than 110MPa and its bearing capacity can reach 75MPa.The degradation performance is only controlled by temperature.At 40-175℃,there is no significant change of the knot in the simulated formation water for 5h,and the degradation rate can reach 100% within 72h.The degradation products are CO_(2)and water.It is applied to 6 well-times in the field with a success rate of 100%.The application of Well B-3 show that the construction pressure of each stage increased greatly after the knots are put into each section for temporary plugging with an average increase of 5.4MPa.Field monitoring results show that the fracture volume increases significantly after temporary plugging,which proves the effectiveness of temporary plugging of the knots.