随钻井旁地质构造体深探测的声源研究和正演模拟

When the rotary steering drilling system has the ability of exploring the deep reservoir interface near borehole and ahead of the bit, and the fracture system trend of near well zone while drilling, we can accurately control the drill bit up and down, left and right, and thus achieve real geo-steering drilling. At present, short detection distance and low resolution of LWD technology severely affect the accurate judgement of formation interface and fracture system near the borehole, which is not conducive for drilling smooth trajectory of wells. Here we propose to use plasma impulse sound source with advantages of high power, wide frequency band, energy accumulated, controllable and repeatable excitation characteristics as the transmitter source in deep exploration while drilling. This source may not only increase the detection range to more than 100 meters for borehole geological structure and the adjacent wells, but also improve the detection resolution of wellbore fracture system. Aiming at the space detection characteristics of acoustic waves, the basic characteristics of electro-acoustic and directional energy accumulation characteristics of acoustic waves are studied experimentally. The forward modeling is carried out by using numerical simulation software, and the adaptability of acoustically permeable materials and electrode structures while drilling is studied. This project integrates drilling, logging, seismic and reservoir development technologies in drilling process. It can be far-reaching, clear-looking, accurate, and fast. It is of great significance to the drilling of wells in rescue wells, as well as the development of shale gas, low permeability oil and gas. Retrieval result shows that the method proposed in this project has not been reported at home and abroad.

当旋转导向钻井系统具备能够随钻深探测井旁和钻头前方的储层界面以及近井带储层裂缝体系走向的能力时，就可以控制钻头钻进的上下、左右方向，从而实现真正随钻地质导向技术。目前随钻探测距离近、分辨率低，不利于光滑井眼的钻成，影响对地层界面及旁裂缝体系判断的准确性。本项目应用等离子体冲激声源作为随钻深探测技术的发射源，其功率大、频带宽、可聚能、可控、可重复激发的特性，不仅将探测距离提高到百米以上，而且可探测井周地质构造和井筒的走向以及提高井旁裂缝体系的探测分辨率。本项目以声波的空间探测特性为目标，实验研究其电声基本特性和定向聚能特性，利用数值仿真软件进行正演模拟，并开展透声材料及电极结构的随钻适应性研究。本项目将钻井、测井、地震和油藏开发技术综合在随钻过程中，可以探得远、看得清、钻得准、打得快，对救援井钻井以及页岩气、低渗油气藏和致密油开发有重大意义。经过检索，本项目提出的方法在国内外未见报道。

当前随钻深探测技术，无法兼顾声源辐射能量、声源频率、空间尺寸限制，方位指向性、方位分辨率和探测距离，无法精确识别较远位置反射体方位。冲激声源深探测技术利用高功率脉冲电源放电电极在水介质中高压放电产生的巨大声脉冲效应，不仅可以对井旁的裂缝进行有效评价，而且可以探测井外数十米甚至更远处的地质构造体，其具备的较高探测分辨率，更有利于对地质结构的探测和成像。本项目以井下三维空间探测特性为目标，构建井下随钻大功率等离子体冲激声源实验平台，实验研究其电声基本特性，并开展其声源发射特性、定向聚能特性和随钻环境适应性的研究，正演模拟了钻头前方地质界面、U型井/救援井、裂缝地层等地质构造在不同声源参数下的冲激声源声场特性，形成以大功率宽频带声源为基础，能够解释百米内近井带不同地质构造、邻近井筒位置的理论体系和方法，并初步解决声源在随钻工程实施时的可实现性问题。