基于不同应力的水力裂缝形态试验研究
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摘要
为了研究压裂后的水力裂缝形态,以相似材料成型的试件为压裂对象,利用水力压裂装置,开展了不同应力条件下的水力压裂试验。研究结果表明:二维应力条件下,水力压裂形成单一裂缝的概率大于复杂裂缝的概率;裂缝形态的复杂性与试验应力有关,当三向应力(最大水平主应力、垂直应力、最小水平主应力)的值相差较大时,容易形成单一裂缝形态;当三向应力中有2个值相近,且均与第3个应力相差较大,则容易形成复杂裂缝形态;复杂裂缝形态中的分支缝与最大水平主应力存在不同的夹角,但均沿平行于最大水平主应力的方向扩展;在同一应力条件下,不同试件压裂产生的裂缝形态也不尽相同,与试件的均质性、压裂液的流动路径、破裂面的特征有关。
To study the fracture morphology, hydraulic fracturing experiments were conducted by means of hydraulic fracturing device and specimen made of similar materials under condition of different stress. The results show that the probability of forming single fracture is greater than that of forming complex fracture morphology under two-dimensional stress conditions. The complexity of fracture morphology is closely related to experimental stress. When the values of triaxial stress(maximum horizontal principal stress, vertical stress, minimum horizontal principal stress) differ greatly, it is easier to form single fracture. While two parameters of them are close and both are different greatly in values, the fracture morphology becomes complex. There is an angle between main fracture and bifurcate fracture and the angle varies in different specimens, the fractures all propagate along the direction of parallel to maximum horizontal stress. Under the same condition, fracture morphology upon different fractured specimens are different from each other, which is related to the homogeneity of the specimen, flow path of fracturing fluid and feature of fractured surface.
To study the fracture morphology, hydraulic fracturing experiments were conducted by means of hydraulic fracturing device and specimen made of similar materials under condition of different stress. The results show that the probability of forming single fracture is greater than that of forming complex fracture morphology under two-dimensional stress conditions. The complexity of fracture morphology is closely related to experimental stress. When the values of triaxial stress(maximum horizontal principal stress, vertical stress, minimum horizontal principal stress) differ greatly, it is easier to form single fracture. While two parameters of them are close and both are different greatly in values, the fracture morphology becomes complex. There is an angle between main fracture and bifurcate fracture and the angle varies in different specimens, the fractures all propagate along the direction of parallel to maximum horizontal stress. Under the same condition, fracture morphology upon different fractured specimens are different from each other, which is related to the homogeneity of the specimen, flow path of fracturing fluid and feature of fractured surface.
引文
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[3]何双喜,王腾飞,严向阳,等.煤层气储层缝网压裂数值模拟分析[J].油气藏评价与开发,2017,7(3):74.
[4]杜春志.煤层水压致裂理论及应用研究[D].徐州:中国矿业大学,2008.
[5]马耕,张帆,刘晓,等.地应力对破裂压力和水力裂缝影响的试验研究[J].岩土力学,2016,37(增2):216.
[6] Rahman M M, Rahman S S. Studies of hydraulic fracture-propagation behavior in presence of natural fractures:Fully coupled fractured-reservoir modeling in poroelasticenvironments[J]. International Journal of Geomechanics, 2013, 13(6):809-826.
[7]孟尚志,侯冰,张健,等.煤系“三气”共采产层组压裂裂缝扩展物模试验研究[J].煤炭学报,2016,41(1):221-227.
[8] Chuprakov D, Melchaeva O, PrioulR..Injection-sensitive mechanics of hydraulic fracture interaction with discontinuities[J]. Rock Mechanics and Rock Engineering,2014, 47:1625-1640.
[9]杨兆中,何睿,李小刚,等.深埋煤层气同步压裂应力干扰机理研究及应用[J].油气藏评价与开发,2017,7(4):65-72.
[10]杨焦生,王一兵,李安启,等.煤岩水力裂缝扩展规律试验研究[J].煤炭学报,2012,37(1):73-77.
[11]程远方,徐太双,吴百烈,等.煤岩水力压裂裂缝形态实验研究[J].天然气地球科学,2013,24(1):134.
[12]陈江湛,曹函,孙平贺,等.三轴加载下煤岩脉冲水力压裂扩缝机制研究[J].岩土力学,2017,38(4):1023-1031.
[13]石欣雨,文国军,白江浩,等.煤岩水力压裂裂缝扩展物理模拟实验[J].煤炭学报,2016,41(5):1145.
[14]马耕,张帆,刘晓,等.裂缝性储层中水力裂缝扩展规律的试验研究[J].采矿与安全工程学报,2017,34(5):993-999.
[15]张帆,马耕,刘晓,等.煤岩起裂压力和水力压裂裂缝扩展机制实验研究[J].煤田地质与勘探,2017,45(6):84-89.