Optimization Design Of The Microseismic Surface Monitoring System In Shale Gas Development

In the shale gas development, hydraulic fracturing is often conduct to produce artificial fracture to improve the exploration efficiency of the low permeability and dense oil and shale gas. Evaluation of the hydraulic fracturing is generally achieved by monitoring induced microseisms. Microseismic monitoring is one of the best techniques to provide accurate, timely and abundant evaluation information for reservoir fracturing. In microseismic monitoring of hydraulic fracturing procedure, the selection of monitoring system plays a very important role in determining the accuracy of microseismic locations as well the number of events to be located, and eventually affects the evaluation of the fracturing.This thesis is focusing on the surface monitoring system. Data collected by the surface monitoring system generally have low signal-to-noise ratio. As a result they are very difficult to identify on wave form. Although data volume is generally very large. We choose the source scanning algorithm to locate microseismic events. The basic principles of source scanning algorithm is discussed along with the basic procedure and the selection of key technical parameters. R=3.0 is proposed as the identification recognition threshold value to distinguish events and noise. Establish the homogeneous isotropic of 3D velocity model, and design a series of theoretical monitoring systems and practical monitoring systems. Adding synthetic microseismic events to noise to form microseismic signals with different SNR levels. By processing the synthetic data, analyzing location results, the optimal design principle of surface monitoring system is obtained.Through the discussion of locating results of monitoring systems with different array layout, layout spacing, layout range, a part of optimized design principle of the surface monitoring system can be concluded. Comprehensive analysis of real monitoring systems is applied to verify the results yielded from theoretical system. Based on the test results, we found that the effect of microseismic location is directly related to the coverage, the number of branches, the spacing of geophones, and the location of source.Preliminary results reveled the following optimization design principle of surface monitoring system: when the number of geophones is the same, the array layout of star shape is generally prefered; Within a certain range, increasing layout range, number of branches, and increasing the spacing of geophones may be favorable to achieve better locating while also control the cost; The radius of monitoring system should be comparable to the size of the depth of source, or slightly larger than the depth of source; If the distribution area of source is roughly known, the geophones of the monitoring system should be focused on the region above the source.Finally, the study analyzed the location results of theoretical monitoring systems and real monitoring systems, together with the analysis of geometric error and travel time error.