【摘要】：薄互層低滲透儲層砂體發(fā)育零散、砂泥交互、縱向?qū)訑?shù)多、厚度薄,壓裂裂縫形態(tài)復雜、難以控制,進而使得注水效果差,有效動用程度低,單井產(chǎn)量低。對其直井壓裂和水平井多級壓裂的耦合滲流規(guī)律和裂縫擴展規(guī)律認識不清,會嚴重制約薄互層低滲透油藏的有效開發(fā)。因此,需針對薄互層壓裂裂縫起裂、擴展規(guī)律和壓裂開發(fā)耦合滲流理論進行深入研究。 本文開展了三向應(yīng)力下裸眼水平井壓裂物模實驗研究：基于薄互層巖心變形破壞特征,建立適用于薄互層井眼起裂判定準則,推導出不同完井方式、不同井型的破裂壓力計算方程；針對不同力學特性砂泥交替的薄互層,建立宏觀平均意義下的薄互層復合巖體本構(gòu)方程,推導了薄互層等效彈性參數(shù)；引入異材參數(shù),基于Griffith斷裂準則和裂縫界面斷裂準則,建立薄互層非平面裂縫起裂-擴展準則,實現(xiàn)裂縫在砂泥界面偏轉(zhuǎn)、滑移、突破等復雜擴展形態(tài)的描述,揭示了薄互層非平面裂縫起裂-擴展規(guī)律。 基于等值滲流阻力法和流場劃分方法,建立了考慮薄互層縱向非均質(zhì)性及壓裂裂縫非平面特征的壓裂直井耦合滲流數(shù)學模型,及考慮射孔、裸眼完井和裂縫相互干擾耦合滲流的水平井多級壓裂滲流數(shù)學模型。針對薄互層整體壓裂注水開發(fā),建立了考慮啟動壓力梯度和壓裂裂縫形態(tài)的薄互層混合井網(wǎng)壓裂三區(qū)耦合流動的兩相滲流模型,實現(xiàn)了不同儲層條件下不同井網(wǎng)壓裂裂縫參數(shù)的優(yōu)化。 研究結(jié)果表明,水平主應(yīng)力差為10MPa時,水平井井筒方位角60°,易生成兩翼對稱的橫切縫；井斜角、方位角、水平主應(yīng)力差越小,破裂壓力越大；層間應(yīng)力差5MPa,隔層厚度6m,均不能實現(xiàn)薄互層上下砂體間溝通；凈總厚度比越大,裂縫非平面性越強,啟動壓力梯度越大,變形系數(shù)越大,薄互層壓裂單井產(chǎn)量越低；當啟動壓力梯度大于0.01MPa/m以后,對產(chǎn)量的影響顯著；當儲層滲透率為1～10mD時,裂縫最優(yōu)導流能力為10～20D·cm;當儲層滲透率超過10mD時,裂縫最優(yōu)導流能力為20～25D·cm。利用本文所建理論模型進行現(xiàn)場應(yīng)用,為薄互層低滲透油藏的壓裂開發(fā)提供了理論依據(jù)。
[Abstract]:The sand body of thin interbedded low permeability reservoir is scattered, sand and mud are interactive, the number of longitudinal layers is more, the thickness is thin, the fracturing fracture form is complex and difficult to control, which makes the water injection effect is poor, the effective production degree is low, and the production rate of single well is low. It is difficult to understand the coupling percolation law and fracture propagation law of vertical well fracturing and horizontal well multistage fracturing, which will seriously restrict the effective development of thin interbed low permeability reservoir. Therefore, it is necessary to deeply study the fracture initiation, propagation law and coupled seepage theory of fracturing in thin interbed fracturing. In this paper, an experimental study on fracturing model of open hole horizontal well under three direction stress has been carried out. Based on the deformation and failure characteristics of thin interbed core, the criteria for determining borehole initiation in thin interbed have been established, and different completion methods have been deduced. The fracture pressure equation of different well types, the constitutive equation of thin interbed composite rock mass with different mechanical properties of sand and mud alternately, the constitutive equation of thin interbed composite rock mass in the sense of macroscopic average, the equivalent elastic parameters of thin interbed, the introduction of different material parameters, Based on the Griffith fracture criterion and fracture interface fracture criterion, the initiation and propagation criteria of thin interbedded non-plane fractures are established to describe the complex propagation forms of fractures such as deflection, slip and breakthrough at the interface of sand and mud. The law of initiation and propagation of thin interbedded non-plane cracks is revealed. Based on the equivalent percolation resistance method and the flow field partition method, a coupled seepage mathematical model considering the longitudinal heterogeneity of thin interbed and the non-plane characteristics of fractured fractures is established, and the perforation is considered. A mathematical model of multistage fracturing seepage in horizontal wells with mutual interference of open hole completion and fracture. Aiming at the whole fracturing and waterflooding development of thin interbed, a two-phase seepage model considering the starting pressure gradient and fracturing fracture form is established, in which the coupling flow in three areas of fracturing of thin interbed mixed well pattern is considered. The fracture parameters of different well pattern are optimized under different reservoir conditions. The results show that when the horizontal principal stress difference is 10MPa, the shaft azimuth angle of horizontal well is 60 擄, and it is easy to generate symmetrical transverse fractures with two wings, and the smaller the angle, azimuth and horizontal principal stress difference, the greater the fracture pressure. The stress difference between layers is 5MPa, the thickness of interlayer is 6m, and the communication between upper and lower sand bodies in thin interbed can not be realized. The larger the net total thickness ratio, the stronger the non-planarity of fracture, the greater the starting pressure gradient, the greater the deformation coefficient and the lower the production of single well in thin interbed fracturing. When the starting pressure gradient is larger than 0.01MPa/m, the effect on production is significant; when reservoir permeability is 1~10mD, the optimal conductivity of fracture is 10 ~ 20D cm, and when reservoir permeability exceeds 10mD, the optimal conductivity of fracture is 20 ~ 25D cm. The field application of the theoretical model in this paper provides a theoretical basis for the fracturing development of thin interbed low permeability reservoirs.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TE357

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