Emerging Geophysical Technologies: Downhole Microseismic Reservoir Monitoring (MRM): A New Instrumentation Technology for Monitoring the Digital Oilfield

Abstract

Abstract As a seismic technology, the microseismic technique is unique in that it provides direct 4D information about the stress changes in the reservoir that are caused by injection and production operations. These changes in stress are common to all producing reservoirs. As a consequence reservoirs emit packets of seismic energy and information about all the small slip events triggered by oilfield operations. It is possible to detect tiny slip magnitudes corresponding to only a few microns of movement. Such movements may correspond to slip on a fracture, movement within the cement, slip on bedding, the opening of a frac or even precursory slip in the completion. Mapping these changes in both space and time provides a unique insight into stress change in the reservoir, the overburden and the well stock. Although this activity is triggered by oilfield activity, the emitted energy derives from strain energy stored within the rock mass. Offshore wireline deployments have shown the value of the microseismic technique and more recent onshore pilots have emphasized the value of permanent sensor installation for reservoir management (Jones et al., 2004). Until very recently microseismic monitoring has been constrained by the requirement to deploy seismic sensors within inactive monitor wells. The recent availability of seismic technology that can be deployed in live wells represents a step-change in our ability to seismically monitor hydrocarbon reservoirs. Such monitoring can now take place even during active injection or production and in offshore environments where monitor wells are rarely available. The key stakeholders in terms of deploying and utilizing the value of this technology include asset managers, engineers involved in production, drilling and reservoir management, together with the seismologists who process the data and deliver value to the reservoir engineer. Microseismic reservoir monitoring represents a new deep-reading technology to understand reservoir processes and thereby better optimize reservoir management and better target field development investment with the goal of producing more oil at a reduced cost. The installation of appropriately designed systems also offers the prospect of combining microseismic monitoring with conventional downhole reflection seismic technology in the form of VSP on demand (Wilson et al., 2004).