Well Targeting Using Joint Geophysical Methods: New Techniques for Exploration and Modelling

Abstract

The objective of this talk is to introduce joint geophysical imaging and its application to earth energy exploration and environmental monitoring. Joint geophysical imaging is the combination of different geophysical methods to produce an accurate model of the earth’s crust. The primary techniques discussed in this talk are seismic wave interpretation and electromagnetic resistivity measurements. This presentation describes (1) the use of microearthquake (MEQ) and resistivity data to locate fluidfilled fracture zones within a geothermal system and (2) the well targeting test cases were these methods were applied. The methods use P- and S-wave velocity, S-wave polarization and splitting magnitude, resistivity and magnetotelluric (MT) -strike directions to determine fracture orientation and porosity. The conceptual approach used to characterize the buried, fluid-circulating fracture zones in hydrothermal systems is based on geological and fracture models. The method has been tested with geothermal field earthquake and resistivity data, core samples, temperature measurements, and more than 3 drilled well. The seismic and electrical measurements used in the drill targeting examples come from portable, multi-station microearthquake (MEQ) monitoring networks, and multi-profile, MT and transient electromagnetic (TEM) observation campaigns. Examples of the methods are first discussed separately. The combined, or “joint”, use of these measurements is based on the fact they share the effects of porosity and fracture induced anisotropy. The successful use of the joint method for targeting is presented for 2 wells, one predicted to be good and one bad.