To compliment traditional P-wave seismic reflection imaging or used as a stand-alone tool, seismoelectric (SE) responses are used as a hydrocarbon indicator for detection of electrically resistive fluids (freshwater, oil & gas) up to approximately 6000 ft. Using a pair of electrodes and a small explosive charge, SE techniques measures the voltage drop as the P-waves passes through the different interfaces. The electrically resistive zones are logged in the field, allowing for near real time analysis of each shot. SE can be used as a standalone hydrocarbon indicator, or be used in conjunction with more traditional seismic data, increasing the odds of finding and developing a productive well. Another advantage of SE is small footprint required to collect data. This makes it ideal for smaller leases that do not have enough acreage to perform seismic reflection surveys.
HOW IT WORKS
When the body wave generated by the shotgun blast moves through electrical resistive fluids, the fluid moves relative to the rock formation. Ions in the electrical resistive fluid are dragged away from their partners bound to the rock and the generated electrical disturbance travels to the surface near the speed of light and is detected by two antenna arrays setup at the surface. A much reduced electrical field is generated in electrical conductive fluid (i.e. salt water). Although used in the groundwater industry for the past two decades, seismoelectrical surveying is a relatively new method for the exploration of oil and gas at this time.