【作者】 李天才；

【导师】 赵金洲；

【作者基本信息】 西南石油大学 ， 油气田开发工程， 2009， 博士

【摘要】 榆林气田是我国鄂尔多斯盆地发现的大型气田,是长庆油田的四大主力气田之一,“西气东输“的主要气源区。对于鄂尔多斯这类低压低渗透油气藏其自然生产能力极差,压裂改造是开发的必备手段,完善发展这类低渗透气藏的高效改造技术,不仅是摆在石油工作者面前的重要课题,也是我国石油工业发展战略的需要。对榆林气田低压气藏压裂工艺及配套技术的研究和完善,不仅可以为该区块的勘探开发提供有力的技术支撑和技术手段,为进一步提高上古低压气藏的单井产量,提高气田的经济综合开发效益起到重要的作用;而且也是针对这类难开发的低渗储层的改造措施方面的一个技术储备,为鄂尔多斯盆地的储层改造提供一个研究思路及借鉴方法。本文从上古储层的实际地质特征入手,针对榆林上古压裂改造技术的需要,重点对压裂定量选井选层技术、多薄层压裂模型、控缝高理论与技术、支撑剂回流机理和压降评估等方面进行了较为系统和深入的研究,取得了以下主要成果:(1)通过榆林上古储层地质特征、前期压裂资料和生产测试资料的统计、评估、分析,运用灰色关联、模糊数学等方法建立了利用人工智能方法提高榆林上古储层压裂效果的定量选井选层模型,形成了一套既考虑储层特征又考虑施工参数优选压裂井层的方法。(2)根据Kirchoff第一定律和Kirchoff第二定律,建立了多层水力压裂过程中的流量分配模型,实现了对整个压裂过程中的流量初始分配和再分配的动态分配;在此基础上考虑多层裂缝同时起裂延伸,建立了多条垂直裂缝三维延伸数学模型,编制了相应的计算程序。(3)利用线弹性断裂力学和数理方程知识,在拟三维的假设条件下,引入动态应力强度因子公式,建立了裂缝高度模型。并编制了程序,进行了该区块裂缝高度延伸影响因素的研究。(4)建立了压裂液返排中的支撑剂回流力学模型和强制返排的井口压力计算模型,为定量确定压裂返排参数、选择最佳的油嘴提供依据:建立了气井生产过程中出砂的力学机理模型。(5)研究与分析传统的压力递减分析模型,对传统G函数分析方法进行了改进,并考虑压裂液的压缩性与压后立即返排,建立了适合裂缝性油藏的PKN和KGD二维分析模型,形成新的压裂分析解释技术。(6)在考虑非达西效应和长期裂缝导流能力的基础上,建立了压裂气井产量预测数学模型,给出了压裂气井产量拟合求取裂缝参数的基本原理,并依据榆林气井压后生产数据拟合得到了支撑裂缝参数。更多还原

【Abstract】 Yulin gas-field, a large gas field found in Ordos basin, one of Changqing’s four main gas fields, is one chief gas resource zone of the West-East Gas Pipeline Project. For the reservoirs with low permeability and formation pressure as Ordos, hydraulic fracturing is an essential approach for improving well production. So improving the effective stimulation technology for low permeability gas resource is researchers’ key subject, and also the Strategic demand of petroleum industrial’s development.Research and improvement of the fracturing techniques and technology for Yulin low pressure gas reservoir can not only provide powerful technology brace and approach, but also can play an important role in improving single well’s output of Palaeoid low pressure gas reservoir and reservoir’s composite economic benefit. Further more, it can also provide technology reserve for low permeability reservoir’s exploitation, a research route and reference for formation stimulation in Ordos basin reservoir.This article starts with the actual geologic characteristic of Palaeoid reservoir, considering the demand of fracturing technology in Yulin, and especially does an in-depth and systemic study on the contents below: the technology of fracturing quantitative selection of well and layer, the model of multi-laminar fracturing, the technology and theory of controlling fracture height, backflow mechanism about proppant, evaluating the pressure drop and so on. The achievements are as follows:(1) Through the statistics, evaluation and analysis on the geologic characteristic of Palaeoid reservoir in Yulin, the early fracturing data and the production test data, with the methods of gray correlative and fuzzy mathematics, we set up a model of quantitative selecting well and layer on enhancing fracturing effect about Palaeoid reservoir in Yulin with artificial intelligence approach, and formed a suit of methods of selecting fracture well and layer, considering reservoir characteristic and treating parameters.(2) Based on Kirchoff’s first law and second law, we established a model of distributing flow in the multi-layer hydraulic fracture process, which successfully achieved the aim of flow’s dynamic distributing for the initial and redistribution. Considering multi-layer fractures extending at the same time, we set up a mathematic model of multi-vertical splits which can extend dimensionally, and compiled a relevant calculation procedure.(3) With the knowledge of linear elastic fracture mechanics and mathematical equations and on the assumption of P3D, we set up a model of fracture height with the introduction of dramatic stress intensity formula, and investigate the factors which can affect the extension of fracture height in this zone.(4) We established a mechanical model of proppant backflow in the process of fracture fluid flowback, and set up a calculating model of wellhead pressure in the course of compulsive flowback, which provide the criterion for checking parameters of fracture flowback and selecting optimal choke. We also built a mechanical model of gas-well’s sand flow during the production.(5) With the research and analysis on traditional model of pressure decline, we improved the traditional method of G function analysis; Considering the fracture fluid’s compressibility and discharging immediately after fracture, we established PKN and KGD models through two-dimensional analysis, and developed a new analyzing and interpreting technology.(6) Based on the consideration of non-Darcy flow and long-term conductivity, we built a mathematical production forecast model of fractured gas-well, put forward the fundamental principle of matching fracture parameters by the gas-well’s production, and fitly got prop-fracture’s parameters through the production data obtained after fracturing.更多还原