【摘要】：近些年來,我國(guó)對(duì)陸上石油的勘探程度及難度不斷增加,低滲透油田越來越受到人們的重視。對(duì)于低滲透油田,人們通常利用水平井分段壓裂技術(shù)來提高油井的產(chǎn)油能力。壓裂水平井提高油層產(chǎn)能的機(jī)理是將普通水平井中原來的流體徑向滲流轉(zhuǎn)變成線性滲流。然而低滲透油藏由于存在啟動(dòng)壓力梯度,會(huì)導(dǎo)致流體出現(xiàn)非線性——擬線性的非Darcy滲流規(guī)律,在不定常滲流過程中壓力擾動(dòng)的傳播存在一個(gè)動(dòng)邊界,這將導(dǎo)致相應(yīng)的不穩(wěn)態(tài)滲流帶有非齊次性和非線性。本文首先明確了低滲透油藏的滲流特征,考慮啟動(dòng)壓力梯度的影響,通過改進(jìn)無量綱壓力定義,結(jié)合復(fù)合線性流動(dòng)理論,建立了考慮啟動(dòng)壓力梯度的垂直裂縫井之雙線性流模型,分別得到井底定產(chǎn)量及定流壓條件下不同啟動(dòng)壓力梯度、導(dǎo)流能力的動(dòng)邊界傳播規(guī)律,以及井底壓力、儲(chǔ)層壓力分布剖面和井底產(chǎn)量圖。計(jì)算分析表明,利用線性復(fù)合模型可以有效地模擬矩形油藏有限導(dǎo)流垂直裂縫井模型,將結(jié)果與精確解進(jìn)行對(duì)比后,結(jié)果發(fā)現(xiàn)該解在前期與精確解擬合情況較好,但在中期滲流階段可能會(huì)產(chǎn)生滲流模型上的差異,即可能的平面徑向流動(dòng)段不會(huì)發(fā)生,代之而來的是平面線性流動(dòng)。在低滲油藏中,動(dòng)邊界傳播速度隨地層的啟動(dòng)壓力梯度的增大而逐漸減慢。對(duì)于固定井底流壓條件,動(dòng)邊界隨著時(shí)間的延長(zhǎng)向外傳播,裂縫中點(diǎn)處動(dòng)邊界傳播速度最快,兩邊逐漸遞減,整體呈坡錐型曲線,達(dá)到最大動(dòng)外邊界后停止傳播;當(dāng)最大動(dòng)邊界滿足xm D=1.0/λD時(shí),單井最大動(dòng)用面積為yf(pi-pwf)/λ;如果地層的啟動(dòng)壓力梯度越大,那么壓降漏斗將會(huì)越陡,同時(shí)產(chǎn)量的遞減速度也將會(huì)越來越快。最后,利用線性復(fù)合模型之不對(duì)稱泄流面積模型、三區(qū)、五區(qū)模型可近似地模擬分段壓裂水平井,得到的解與數(shù)值模擬的結(jié)果對(duì)比,給出了解析解模型的適用范圍。
[Abstract]:In recent years, the degree and difficulty of onshore oil exploration in China has been increasing, and people pay more and more attention to low permeability oil fields. For low permeability oil fields, horizontal well subsection fracturing technology is usually used to improve the oil production capacity of oil wells. The mechanism of fracturing horizontal well to improve reservoir productivity is to transform the original fluid radial seepage into linear seepage in ordinary horizontal well. However, due to the existence of start-up pressure gradient in low permeability reservoir, the fluid will appear nonlinear-quasilinear non-Darcy seepage law, and there is a moving boundary for the propagation of pressure disturbance in the process of unstable seepage, which will cause the corresponding unstable seepage to be non-homogeneous and nonlinear. In this paper, the seepage characteristics of low permeability reservoir are clarified, and the influence of starting pressure gradient is considered. by improving the definition of dimensionless pressure and combining with the compound linear flow theory, the bilinear flow model of vertical fracture well considering starting pressure gradient is established, and the dynamic boundary propagation law of different starting pressure gradient and diversion capacity under the condition of constant bottom hole production and constant flow pressure, as well as the bottom hole pressure, are obtained respectively. Reservoir pressure distribution profile and bottom hole production map. The calculation and analysis show that the linear composite model can effectively simulate the finite conductivity vertical fracture well model of rectangular reservoir. After comparing the results with the exact solution, it is found that the solution fits well with the exact solution, but the difference in the seepage model may occur in the middle seepage stage, that is, the possible plane radial flow section will not occur, but the plane linear flow will be replaced by the solution. In the low permeability reservoir, the propagation velocity of the moving boundary slows down with the increase of the starting pressure gradient of the formation. For the fixed bottom hole flow pressure condition, the moving boundary propagates outward with the prolongation of time, the propagation speed of the moving boundary at the midpoint of the fracture is the fastest, the two sides decrease gradually, and the whole slope cone curve stops when the maximum moving boundary satisfies xm D 鈮，

本文編號(hào)：2501727