致密油藏水平井同井缝间注采机理研究

Aiming at the problems such as low plane and vertical sweep efficiency, quick decline in production and uneven pressure condition between production and injection, we put forward a method of injection and production between hydraulic fractures in a horizontal well, which is, through the installation of separation devices of injection and production and injection valves, to transform the interwell displacement into displacement between fractures. Compared with the conventional injection and production well pattern development mode, the development method proposed in this paper can obviously improve plane and vertical sweep efficiency in SRV, strengthen the flooding effect, establish an effective flooding system, and increase the horizontal well production.In this paper, we will carry out the physical simulation experiment and combine the real-time scanning detection technology of NMR to find out the microscopic distribution of the injected fluid in the fracture, reveal the static and dynamic characteristics of the water and water surfactant in the reservoir and the low pressure injection, the reservoir expansion mechanism under low pressure injection. Then we establish a mathematical model which takes microfracture expansion, fracture closure in shutting period, reservoir imbibition and expansion mechanism. After that, we design an asynchronous injection production process and control system to achieve unbalanced adjustment of injection production between fractures. The characteristics of the study are to transform the interwell problem into the interstage problem, and to find out the flow mechanism of the horizontal well and the well between the wells and the formation of mathematical model. The research results are of great theoretical and practical significance for the effective development of compact reservoirs under low oil prices.

目前致密油藏井间注水开发方式波及体积小、产量递减快、不能建立有效驱替系统，本项目提出水平井同井缝间注采方法，即通过注采分隔装置和注采阀，进行同井缝间注采，将井间驱替问题转化为缝间驱替问题。相对于常规注采井网，该开发方式能明显提高压裂改造区平面和纵向动用程度，强化驱油效果，较大幅度提高水平井产量。本项目拟开展物理模拟实验，采用核磁实时扫描检测技术，弄清注入流体在裂缝中的微观分布规律，揭示水、水+表面活性剂在储层中的静态及动态渗吸特征和低于破裂压力注入下储层的扩容机理，建立考虑注入阶段天然微裂缝扩展、闷井阶段裂缝闭合、储层渗吸及扩容机理的渗流模型。通过同一管柱异步注采工艺及控制系统，实现缝间注采量的不均衡调节。研究特色是弄清致密油藏水平井同井缝间注采的渗流机理，形成缝间注采的渗流数学模型及开发方式，取代目前井间渗流理论。研究成果对于低油价下致密油藏有效开发具有重要的理论及实际指导意义。

致密油藏渗透率低，导致注水困难、注入量小、波及效率低、能量补充不充分等难题。本项目提出水平井同井缝间注采方法，即通过注采分隔装置和注采阀，进行同一口水平井缝间注采。在前期研究的基础上，对水平井同井缝间注采工艺进行改进，设计了三种新的井下注采控制装置。研究了水平井同井缝间注采不同开发阶段的驱油机理，厘清了缝间油水的渗流特点及压力传播规律。注入水的渗吸作用是异步注采焖井阶段重要的采油机理，通过室内实验重点探究了渗吸压力对于渗吸采收率的影响，为多级压力水平井同井缝间注采的焖井时间设计提供依据。根据我国鄂尔多斯盆地致密油藏建立了数值模拟模型，研究了储层物性参数、压裂工艺参数和注采参数对水平井同井缝间注采开发效果的影响。目前，该方法已经在长庆油田和大庆油田进行了初步应用，结果表明该方法确实能够较好地改善致密油藏的开发效果。.在水平井缝间注采的基础上，本研究团队提出了水平井分段异步注采的开发新模式，研究了气体作为注入介质时的开发效果。同时将传统水平井注气吞吐与水平井分段异步注采方式相结合，对压裂参数和注采参数进行了敏感性因素分析。在新模式下，水平井将分为注入段、采油段、分隔段三段，与传统的水平井注气吞吐相对比，具有更好的能量补充效果。本研究为我国致密油开发提供了一种极具潜力的开发方式，为致密油藏合理高效开发提供理论依据和技术支持。