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本文以鄂尔多斯盆地安塞油田王窑区长6低渗透砂岩油藏为例,研究了在油藏注水开发过程中形成的注水诱导裂缝特征及其形成机理,探讨了注水诱导裂缝对低渗透油藏注水开发调整的影响。注水诱导裂缝是指低渗透油藏在长期注水开发过程中由于注水压力过高形成的以水井为中心的高渗透性开启大裂缝。注水诱导裂缝主要表现为张裂缝,其规模大,延伸长,一般沿着主渗流裂缝方向或现今地应力方向延伸和扩展,并随着低渗透油藏注水开发,注水诱导裂缝不断地扩展和生长。注水诱导裂缝的渗透率高,沿诱导裂缝方向容易造成油井的快速水窜和水淹。注水诱导裂缝通常有3种形成机制,其中由于注水压力超过天然裂缝开启压力,导致天然裂缝张开、扩展和延伸,形成开启的大裂缝是研究区裂缝的主要成因机理。注水诱导裂缝形成以后,彻底改变了低渗透油藏的渗流场和压力场,影响低渗透油藏的注水开发效果,同时给低渗透油藏的中高含水期注水开发及其调整带来一系列更深层次问题,需要引起重视。
Taking the Chang 6 low permeability sandstone reservoir in Wangyao area of Ansai Oilfield, Ordos Basin, as an example, the characteristics of water-induced fractures and their formation mechanism during water flooding in reservoirs have been studied. The effects of water-induced fractures on low permeability reservoirs Impact of waterflood development and adjustment. Water-induced fractures refer to the high-permeability fractures centered on wells in the formation of long-term water flooding in low-permeability reservoirs due to the high water injection pressure. The water-induced fractures are mainly composed of Zhang fractures, which are large in scale and extended in length and generally extend and extend along the direction of the main seepage fractures or the current direction of earth stress. With the development of water injection in low-permeability reservoirs, water-induced fractures continue to expand and grow . Water infiltration induced fracture permeability, along the direction of the induced fracture easily lead to rapid water channeling and flooding. Water-induced fractures usually have three kinds of formation mechanisms. The natural fractures open, extend and extend due to the pressure of water injection exceeding the natural cracking open pressure. The formation of large open fractures is the main cause of the fractures in the study area. After the formation of water-induced fractures, the seepage field and pressure field of low-permeability reservoirs are completely changed, which will affect the waterflooding development effect of low-permeability reservoirs. At the same time, a series of deeper waterflooding development and adjustment will be brought to low-permeability reservoirs Hierarchy issues need to be taken seriously.