摘要
2008年5月12日14时28分,我国汶川发生了举世震惊的8.0级特大地震,给人民群众的生命财产造成重大损失,党中央、国务院对此高度重视,立即成立了国务院抗震救灾指挥部。为了研究地震的发震机理以及进行地震监测和预报,国土资源部会同科技部和中国地震局组织实施汶川地震断裂带科学钻探工程。汶川地震断裂带科学钻探的研究内容,是在龙门山北川—映秀断裂及龙门山前缘安县—灌县断裂附近实施5口科学群钻的基础上,开展地质构造、地震地质、岩石力学、化学物理、地震物理、流体作用和流变学等多学科研究。对大地震和复发微地震的源区进行多学科观测和测试,揭示控制断裂作用及地震发生的物理和化学作用。综合地球物理测井、岩心以及通过主动震源地震成像和观测,识别活动断裂各种构造要素,测量断裂破坏带的宽度和破坏强度,确定断裂的构造属性。并在孔内安放仪器,建立长期的地震观测站。汶川地震断裂带科学钻探一号孔(WFSD-1)在孔深585米时钻遇断层泥,孔壁严重失稳,先后两次发生恶性卡钻事故,迫不得已进行侧钻,严重制约了整个项目的进度。无论是从事地质岩心钻探,还是从事石油钻井的工程技术人员,在过去几乎都没有在大地震发生不久后在断层泥地层钻探取心的经历。在WFSD-1孔钻探施工中,解决断层泥地层取心钻进问题,对钻探技术人员来说是一个新课题。对断层泥孔段孔壁稳定性基本力学机理、孔壁破坏准则、坍塌压力和破裂压力的计算以及影响孔壁稳定的因素进行了分析。并对断层泥的物质组成及其理化性能进行了试验测试分析,得出断层泥的原始含水率较低、分散性很强、渗透率很低及吸水易膨胀的结论;同时也通过试验测试了断层泥在原始含水率状态及风干状态下的无侧限抗压强度,以及断层泥在不同含水率状态下的抗剪强度,得出断层泥的含水率对其无侧限抗压强度和抗剪强度有很大的影响,随着含水率的增加,其无侧限抗压强度和抗剪强度急剧下降。通过对断层泥孔段孔壁稳定性基本力学机理的分析,以及对断层泥的理化性能和物理力学性能的试验测试研究等,提出了断层泥钻探面临的问题,即:(1)高地应力引起断层泥发生塑性流动,从而使得钻孔缩径;(2)断层泥吸水发生体积膨胀引起钻孔缩径;(3)由于断层泥的强粘滞性以及强分散性,容易发生压差粘滞卡钻。针对上述三点问题,进而提出了相应解决思路及泥浆技术对策,即:(1)提高泥浆的比重,增大泥浆液柱压力来平衡高地应力;(2)降低泥浆的失水量且实现泥浆低渗透性,来抑制断层泥吸水膨胀;(3)提高泥浆的润滑解卡性能,使其在钻进时具有良好的润滑性,发生卡钻时具有一定的解卡性能。针对提出的泥浆技术对策,专门开发了适应小口径取心钻探并具有稀释成膜特点的的处理剂,并通过大量试验甄选出与之相配伍的其他处理剂,最终研制出了具有良好沉降稳定性、较低失水量和渗透性的高比重低失水低渗透泥浆体系,应用于汶川地震断裂带科学钻探一号孔,取得了立竿见影的效果,为整个项目的顺利推进奠定了坚实的基础。
At 14:28 on May 12,2008,it took place 8.0 earthquake shocked the world in Wenchuan of China, and it caused heavy losses to people’s lives and property. State Council attaches great importance to it, and set up state council earthquake relief headquarters immediately. In order to study the mechanism of the earthquake and seismic earthquake monitory and prediction, ministry of land and resources joint China Seismological Bureau to organize the earthquake fault scientific drilling project. The content of the earthquake fault scientific drilling project researching is on the basis of five scientific drilling groups on the Beichuan-Yinxiu in the Longmen Mountains and the rupture front of Longmen Mountains Anxian-Guanxian, carried out multi-disciplinary research with geological structure, earthquake geology, rock mechanics, chemical physics, earthquake physics, fluids, rheology and so on. Observation and testing source of the large earthquake and micro multi-disiplinary earthquake, revealing the physical and chemical effects of the controlling faulting and earthquake occurring. Integrated geophysics logging, coring imaging and observation through active source seismic. Indentify active faults of various structural elements, measuring the width of fracture failure and strength, and determine the structural properties of fracture. Established Long-term seismic station by placing instruments in the hole,. The first hole of Wenchuan Earthquake Scientific Drilling Project(WFSD-1)encountered gouge when it is 585 meters deep, hole serious instability, malignant sticking twice accident, forced to sidetrack, seriously hampered the progress of the project.No matter the engineers and technicians who engage in geological core drilling and oil drilling didn’t have the experiences about core drilling in fault gauges wall after great earthquake. This is a new subject for drilling technical personnel to solve the problem core in the section of fault gauges during the process of WFSD-1.We analysis the fundamental mechanism, failure criterion of wall, computation of collapse pressure and fracture pressure , the factor affect wall stability of the fault gauges section of the wall. And analysis the constouctional material and Physicochemical Properties of the fault gauges by experiment and reach a conclusion that the fault gauges have low original water Content, strong disparity, low permeability, easy to absorb water and volume expanding. At the same time we test the unconfined compression of the fault gauges in original water content and air-dried condition. Also test the shear strength of the fault gauges in different water content, draw a conclusion that the water content have a great influence on the unconfined compression and shear strength of the fault gauges, with the water content was increasing, the unconfined compression and shear strength decline sharply.We put forward the problems of the fault gauges drilling through analysis the fundamental mechanism about wall stability and study on the Chemistry and physic mechanics of fault gauges, they are:(1) High crustal stress causes fault gauges plastic flow, result for shrinking pathway of hole.(2) Volume expansion by the fault gauges absorbs water result for shrinking pathway of hole.(3) It easy to sticking as high viscosity and high disparity of he fault gauges.To solve these problems, this paper presents the solution and mud technical of the problems, they are:(1) Increase the density and fluid column pressure of the mud to balance high crustal stress.(2) Lower the filtrations of the mud result for achieve low filtration to bring down fault gauges absorbs water.(3) Strong the lubricity and the sticking-Proof capacity of the mud while drilling have good lubrication, if sticking it can solve the problem.Aimed at solve the question, we developed the drilling mud additives can dilute and film-foaming that suit for small hole wire line drilling exploration, And screen out another additives that have the best compatibility proportion with it. Finally we developed the mud system which has good stability, low filtration, heavy density, and apply to the first drilling hole of the Wenchuan earthquake fault science project (WFSD-1) and achieve good results, laid the groundwork for the projects Completed Smoothly.