Application Of Micro-seismic Monitoring And Simulation Technology In The Research Of Fracture

The research of real-time microseismic monitoring used in the waterflood swept area of the oil field and hydraulic fracture is in the ascendant. How to complete automatic monitoring, to improve sensitivity of system and locate precisely in real time are three difficult problems before the technology is used widely. In order to resolve these problems, an independent-developed microseismic monitoring system called MEMS has been developed to aim at this international problem. The system was composed of three components MEMS geophone which was the core hardware, and GPS system that was used to do real-time locating and time service. The digital recording and processing software according with the hardware system and monitoring has been compiled, and automatic monitoring function in network has been realized. Otherwise, the system of computer discriminatory standard and real-time locating concept has been developed and automatic data processing and seismic focus calculating has been realized at the same time.The rock sample will generate acoustic emission when it was suffering the external or internal loading. The mechanism and process of rock failure was used to study by analyzing acoustic emission. In this paper, through analyzing the signals of acoustic emission under monoaxial compression loading, the total failure process of sample was carefully divided into four procedures. With the loading increasing, the events of acoustic emission gradually increased with the strain changing in the first and began to decrease afterwards before the sample faulting totally. The energy of acoustic emission continuously increased to the maximum when the sample faulting totally. The frequency of acoustic emission was generally the content 0-800Hz. At the same time, the MEMS geophone can be used to monitor the microseismic event of coal mining, water reservoir and hydraulic fracturing through the research of failure location and the ratio of rock fracture can be predicted by counting numbers of acoustic emission.After spent six months to monitor injecting microseism in Ying 11 block of DongXin field using this system and collect abundant microseismic wave files. The result showed that the orientation of injecting fracture was mainly NE90°to NE125°. The maximum horizontal principal stress directions were mainly distributed in NE90°-NE130°range. Analysis of numerical simulation result of reservoir stress in Ying 11 block showed that the maximum horizontal principal stress directions are approximate east-west in central and western region and approximate NE130°at eastern border. It was coincide well between simulated results and monitoring fracture direction.The calculation error analysis of fracture showed that the monitoring result can be controlled in a reasonable extent. Therefore, this system can be further developed to provide important practical reference for the policy and distribution of production in low permeability oil field.Hydraulic fracturing in oilfield is an important means of transforming low-permeability reservoirs. The energy of rock failure in hydraulic fracturing is higher than water-flood in oilfield, so it is more conducive to monitoring. In oilfield production process, how long the crack is and how the crack of the fractured wells to extend after hydraulic fracturing cannot estimate at the present time. At the same time, the direction of the crack and the connectivity with wells surrounding can not be immediately resolved. So, a micro-earthquake monitoring test of hydraulic fracturing was carried out in XinChang and MaJing zone of XiNan Oil and Gas Company. The reliable three-dimensional image of the cracks was gained. At the same time, the research showed that hydraulic cracks growth rate is uneven in the process of the hydraulic fracturing in different times and the crack growth rate was greatly speedy at the beginning of the period and then slowed. Usually, the wings of cracks were often asymmetric and the crack is basically vertical.Result shows that there was an important relationship between failure of rock and crystal structure and composition and crystal structure of reservoir bed also affects the breakdown of rocks. The macroscopic and microscopic cracks both extended on a Z-shape in the process of hydraulic fracturing and depended on the specific model of rock properties in reservoir. The velocity of the wave in stratum was impact by rock and water saturation and the wave velocity of the water-saturated rock was bigger generally than that of dry rock and the relationship in rock saturated with oil and gas needed be further studied. The crack of rock was also impacted by the chemical acting each other of water and rock in reservoir. On the one hand, it can enhance the rupture strength of rock and on the other hand may also reduce the breakdown strength. The specific impact depended on the structure and composition of rock and formation and the chemical nature of formation water. In addition, the geothermal field can also play an important supporting role in fracture process. The porosity in rock cracks increases under high-temperature and aggravates accordingly the chemical acting each other of water and rock in reservoir. In short, this paper reported micro-earthquake induced by oil field water injection or hydraulic fracturing monitoring used by self-developed micro-seismic monitoring system and the monitoring results can be a reasonable explanation for the development of cracks, and this technology is of great values in the future oilfield production.