【摘要】：海拉爾油田屬于復雜斷塊油田,部分區(qū)塊儲層物性差,水井壓裂后仍難以實現(xiàn)有效注入。因此,開展了低產井壓裂提高單井產量技術研究很有必要。而常規(guī)壓裂形成的對稱雙翼裂縫改造體積有限,不能充分動用致密油氣資源,多分支壓裂技術可有效解決上述問題。但目前對近井多分支壓裂技術的起裂機制及影響因素認識不清,為此本文運用有限元方法,利用comsol軟件對多分支縫起裂機理進行模擬研究,主要工作及認識如下:1、考慮初次壓裂誘導應力對近井地帶應力場的作用,建立多分支縫起裂角及起裂壓力的力學計算模型。應用有限元軟件實現(xiàn)了近井區(qū)域裸眼井眼壓裂機理、全尺寸單縫壓裂機理、近井區(qū)域單縫壓裂機理、近井區(qū)域多分支縫壓裂機理的數值模擬分析。2、根據有限元數值模擬結果,確定了初始縫的起裂點、第一條分支縫、第二條分支縫的起裂點和凈壓力。3、初始縫的起裂點在井壁上,且垂直于最小水平主應力,符合經典理論觀點。該起裂點稱為起裂點1A。第一條分支縫在初始縫尖端、初始縫縫體中部和井眼上。三個起裂點分別定義為2A、2B、2C。在第一條分支縫全堵和局部半堵時,端部的應力集中是不存在,即起裂點2C不存在。在初始縫全堵條件下,第一條分支縫在初始縫全堵柔性支撐區(qū)中部和井眼上起裂。在初始縫半堵條件下,第一條分支縫在初始縫全堵柔性支撐區(qū)到井眼的中部和井眼上起裂。4、第二條分支縫在井眼上、第一條分支縫縫體中部、初始縫縫體中部、第一條分支縫尖端。五個起裂點分別定義為3A、3B、3C、3D、3E。在第二條分支縫全堵和局部半堵時,端部的應力集中是不存在,即起裂點3D和3E不存在。此時第二條分支縫在井眼上的起裂點3A和裂縫中部的起裂點3B和3C起裂或者延伸。
[Abstract]:Hailaer oilfield belongs to complex fault block oilfield, some blocks have poor physical properties, and it is still difficult to realize effective injection after well fracturing. Therefore, it is necessary to study the technology of fracturing and improving single well production in low production wells. However, the symmetrical double-wing fracture formed by conventional fracturing is limited in volume and can not fully utilize dense oil and gas resources. The multi-branch fracturing technology can effectively solve the above problems. However, there is no clear understanding of the fracture initiation mechanism and its influencing factors in the near well and multi-branch fracturing technology. In this paper, finite element method is used to simulate the fracture initiation mechanism of multi-branched fractures using comsol software. The main work and understanding are as follows: 1. Considering the effect of the initial fracturing induced stress on the stress field in the near well zone, the mechanical calculation model of the fracture initiation angle and the initiation pressure of the multi-branch fractures is established. Using finite element software, the mechanism of open hole fracturing in near-well region, the mechanism of full-size single fracture fracturing, and the mechanism of multi-branch fracture fracturing in near-well area are analyzed by numerical simulation. 2. According to the results of finite element numerical simulation, The starting point of initial fracture, the first branch joint, the starting point and net pressure of the second branch joint are determined. The starting point of initial fracture is on the shaft wall and perpendicular to the minimum horizontal principal stress, which is in line with the classical theory. The starting point is called the initiation point 1A. The first branch is at the tip of the initial fracture, the middle of the initial fracture and the hole. The three initiation sites are defined as 2An 2BX 2C respectively. When the first branch joint is completely plugged and partially plugged, the stress concentration at the end of the joint does not exist, that is, the initiation point 2C does not exist. Under the condition of full plugging of initial fracture, the first branch fracture starts to crack in the middle of the flexible support area of the initial fracture. Under the condition of half plugging of initial fracture, the first branch fracture starts at the middle of the initial fracture and on the middle of the hole, the second branch fracture on the hole, the first branch fracture at the middle of the first branch fracture, the middle of the initial fracture body, and the middle of the initial fracture body. The first branch seams the tip. The five initiation sites are defined as 3An 3BX 3CX 3DX 3E respectively. When the second branch joint is completely plugged and partially plugged, the stress concentration at the end of the joint does not exist, that is, the initiation point 3D and 3e do not exist. The starting point 3A of the second branch fracture on the hole and the starting point 3B and 3C of the middle of the fracture begin or extend.
【學位授予單位】：東北石油大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TE357
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本文編號：2192818