多段壓裂水平井壓力計(jì)算及分析方法
發(fā)布時(shí)間：2018-10-26 09:26
【摘要】：在致密油氣及頁巖氣等低滲透和特低滲透油田的開采中,其儲(chǔ)層自然產(chǎn)能低,必須通過儲(chǔ)層改造才可能達(dá)到工業(yè)油氣流的標(biāo)準(zhǔn)。水平井及其分段壓裂作為一種致密油氣藏開發(fā)的有力手段,能有效增大油氣接觸面積進(jìn)而提高油氣產(chǎn)能,因此近幾年來在低滲透油氣田中得到迅速發(fā)展和廣泛應(yīng)用。由于低滲透儲(chǔ)層的致密性,其壓裂改造難度很大,成本很高,因而對(duì)壓裂施工方案進(jìn)行優(yōu)化設(shè)計(jì)是致密儲(chǔ)層高效和經(jīng)濟(jì)開采的關(guān)鍵,如根據(jù)儲(chǔ)層的特征進(jìn)行水平井的布井,以及對(duì)水平井壓裂段數(shù)和裂縫半長的優(yōu)化。同時(shí)本文的研究涉及到滲流方程解析和數(shù)值方法,對(duì)計(jì)算滲流力學(xué)方法,有一定的指導(dǎo)意義。本文的研究如下： 首先,針對(duì)油井多段壓裂水平井建立方程,運(yùn)用Newman乘積法得到了直井和水平井的單裂縫解析解。為了將單裂縫解推廣到多段壓裂井,我們建立了二維模型,并假設(shè)各個(gè)裂縫的流量并不等于其長度比,建立多段壓裂水平井方程,求解各裂縫流量和井底壓力隨時(shí)間的變化。求解的結(jié)果表明,在流動(dòng)的前期,裂縫長度與其流量基本成正比；而在流動(dòng)的后期,裂縫流量基本與長度無關(guān),影響裂縫流量的主要是裂縫分布位置。因此,建議水平井壓裂應(yīng)盡可能使裂縫長度一致,位置均勻分布。 其次,本文考慮了真實(shí)氣體狀態(tài)方程對(duì)頁巖氣狀態(tài)進(jìn)行描述,用Langmuir吸附對(duì)頁巖氣體吸附和解析吸附現(xiàn)象進(jìn)行描述,并考慮了氣體壓敏效應(yīng),定義了頁巖氣標(biāo)準(zhǔn)壓力,最終得到了頁巖氣多段壓裂水平井的解析解。在計(jì)算過程中,為了加快計(jì)算速度,采用了GPU加速計(jì)算技術(shù),從而得到頁巖氣井底壓力及其導(dǎo)數(shù)隨時(shí)間的變化并討論了吸附系數(shù),儲(chǔ)容比等參數(shù)對(duì)于頁巖氣開采中的井底壓力的影響。 再次,為了克服上述解析方法的局限即必須矩形邊界并且井與邊界必須平行的限制,提出了復(fù)雜油氣儲(chǔ)層水平井多段壓裂非結(jié)構(gòu)PEBI網(wǎng)絡(luò)劃分方法及有效裂縫半長,并在此基礎(chǔ)上實(shí)現(xiàn)了滲流方程的有限體積離散。針對(duì)離散后線性方程組具有稀疏性、不規(guī)則性、大規(guī)模性及非對(duì)稱性的特點(diǎn),采用預(yù)處理的GMRES進(jìn)行求解,并研發(fā)了相應(yīng)的數(shù)值模擬程序。通過與數(shù)值解相對(duì)比,驗(yàn)證了解析解的正確性。最后將本文的結(jié)論運(yùn)用到某油田,并對(duì)一口井例在不同裂縫半長和角度下進(jìn)行模擬,同時(shí)給出了具體的優(yōu)化建議。在實(shí)際應(yīng)用中發(fā)現(xiàn),當(dāng)水平井較長且裂縫較多時(shí),水平井多段壓裂井底壓力可近似為帶有負(fù)表皮的水平井。
[Abstract]:In the production of low permeability and ultra-low permeability oil fields such as tight oil and gas and shale gas, the natural productivity of its reservoir is low, so it must be reformed in order to meet the standard of industrial oil and gas flow. Horizontal well and its fracturing, as a powerful means to develop a tight reservoir, can effectively increase the contact area of oil and gas and increase the productivity of oil and gas, so it has been rapidly developed and widely used in low permeability oil and gas fields in recent years. Because of the compactness of low permeability reservoir, it is very difficult and expensive to reconstruct fracturing, so the optimization design of fracturing operation scheme is the key to high efficiency and economic exploitation of tight reservoir, such as well layout of horizontal well according to reservoir characteristics. And the optimization of fracturing section number and fracture half length of horizontal well. At the same time, the research of this paper involves the analytical and numerical methods of seepage equation, which has certain guiding significance for the calculation of seepage mechanics method. The research in this paper is as follows: firstly, the analytical solutions of single fracture of straight well and horizontal well are obtained by using Newman product method to establish the equation for multi-stage fracturing horizontal well. In order to extend the single fracture solution to multistage fracturing wells, a two-dimensional model is established, and assuming that the flow rate of each fracture is not equal to its length ratio, the multistage fracturing horizontal well equation is established to solve the variation of fracture flow rate and bottom hole pressure with time. The results show that in the early stage of flow, the crack length is proportional to the flow rate, but in the later stage of flow, the crack flow is basically independent of the length, and the crack distribution is mainly affected by the crack flow. Therefore, it is suggested that the fracture length should be consistent and the position should be uniformly distributed in horizontal well fracturing as far as possible. Secondly, the state of shale gas is described by the equation of state of real gas, the phenomenon of adsorption and desorption of shale gas is described by Langmuir adsorption, and the pressure sensitive effect of gas is considered, and the standard pressure of shale gas is defined. Finally, the analytical solution of multistage fracturing horizontal well of shale gas is obtained. In order to speed up the calculation process, the GPU accelerated calculation technique is used to obtain the variation of the bottom hole pressure and its derivative of shale gas with time, and the adsorption coefficient is discussed. The effect of reservoir capacity ratio and other parameters on bottom hole pressure in shale gas production. Thirdly, in order to overcome the limitation of the above analytical method, that is, the rectangular boundary must be restricted and the well and the boundary must be parallel, the method of dividing the unstructured PEBI network and the effective fracture half length of the multi-section fracturing in horizontal wells of complex oil and gas reservoir are proposed. On this basis, the finite volume discretization of seepage equation is realized. Aiming at the characteristics of sparse, irregular, large-scale and asymmetric linear equations after discretization, the preprocessing GMRES is used to solve the problem, and the corresponding numerical simulation program is developed. The correctness of the analytical solution is verified by comparison with the numerical solution. Finally, the conclusion of this paper is applied to a certain oil field, and a well example is simulated under different fracture half-length and angle, and some specific optimization suggestions are given at the same time. In practical application, it is found that when the horizontal wells are longer and have more fractures, the bottom pressure of multi-section fracturing wells in horizontal wells can be similar to that of horizontal wells with negative skin.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TE357
本文編號(hào)：2295275
[Abstract]:In the production of low permeability and ultra-low permeability oil fields such as tight oil and gas and shale gas, the natural productivity of its reservoir is low, so it must be reformed in order to meet the standard of industrial oil and gas flow. Horizontal well and its fracturing, as a powerful means to develop a tight reservoir, can effectively increase the contact area of oil and gas and increase the productivity of oil and gas, so it has been rapidly developed and widely used in low permeability oil and gas fields in recent years. Because of the compactness of low permeability reservoir, it is very difficult and expensive to reconstruct fracturing, so the optimization design of fracturing operation scheme is the key to high efficiency and economic exploitation of tight reservoir, such as well layout of horizontal well according to reservoir characteristics. And the optimization of fracturing section number and fracture half length of horizontal well. At the same time, the research of this paper involves the analytical and numerical methods of seepage equation, which has certain guiding significance for the calculation of seepage mechanics method. The research in this paper is as follows: firstly, the analytical solutions of single fracture of straight well and horizontal well are obtained by using Newman product method to establish the equation for multi-stage fracturing horizontal well. In order to extend the single fracture solution to multistage fracturing wells, a two-dimensional model is established, and assuming that the flow rate of each fracture is not equal to its length ratio, the multistage fracturing horizontal well equation is established to solve the variation of fracture flow rate and bottom hole pressure with time. The results show that in the early stage of flow, the crack length is proportional to the flow rate, but in the later stage of flow, the crack flow is basically independent of the length, and the crack distribution is mainly affected by the crack flow. Therefore, it is suggested that the fracture length should be consistent and the position should be uniformly distributed in horizontal well fracturing as far as possible. Secondly, the state of shale gas is described by the equation of state of real gas, the phenomenon of adsorption and desorption of shale gas is described by Langmuir adsorption, and the pressure sensitive effect of gas is considered, and the standard pressure of shale gas is defined. Finally, the analytical solution of multistage fracturing horizontal well of shale gas is obtained. In order to speed up the calculation process, the GPU accelerated calculation technique is used to obtain the variation of the bottom hole pressure and its derivative of shale gas with time, and the adsorption coefficient is discussed. The effect of reservoir capacity ratio and other parameters on bottom hole pressure in shale gas production. Thirdly, in order to overcome the limitation of the above analytical method, that is, the rectangular boundary must be restricted and the well and the boundary must be parallel, the method of dividing the unstructured PEBI network and the effective fracture half length of the multi-section fracturing in horizontal wells of complex oil and gas reservoir are proposed. On this basis, the finite volume discretization of seepage equation is realized. Aiming at the characteristics of sparse, irregular, large-scale and asymmetric linear equations after discretization, the preprocessing GMRES is used to solve the problem, and the corresponding numerical simulation program is developed. The correctness of the analytical solution is verified by comparison with the numerical solution. Finally, the conclusion of this paper is applied to a certain oil field, and a well example is simulated under different fracture half-length and angle, and some specific optimization suggestions are given at the same time. In practical application, it is found that when the horizontal wells are longer and have more fractures, the bottom pressure of multi-section fracturing wells in horizontal wells can be similar to that of horizontal wells with negative skin.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TE357
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