A Time Domain Update Method for Reservoir History Matching of Electromagnetic Data

Abstract

Technology has fundamentally changed the oil and gas industry enabling it to extract substantial amounts of unconventional resources such as shale gas that were previously non-recoverable or uneconomical to extract. With the development and acquisition of 4D seismic data, engineers have been able to more accurately map out accurately the evolution of fluids within the reservoirs. However, they have encountered the challenge to distinguish between hydrocarbons and injected fluids. Electromagnetic methods have attracted in the last decade substantial interest to exploit the sharp resistivity contrast between hydrocarbons and water, enabling it to track water fluid fronts, optimize injection, thus improving production rates. Conventional approaches to incorporate electromagnetic data into history matching processes have been to invert these data for reservoir parameters and apply those as constraints in the matching process. This approach faces however the challenge that the computational resources required for the inversion may be significant in addition to the requirement for manual postprocessing to ensure meaningful interpretation. In this work we present a novel approach for incorporating a full wave electromagnetic time domain solver in which electromagnetic data are directly included in the history matching process. The full wave modeling enables higher accuracy representation of the underlying structures and its inclusions returns significantly better matchings and forecasts. Introduction Reservoir management has become a quintessential element for coping with the ever increasing demand of emerging countries such as China, Brazil and India and the increasingly more cost-intensive and complex extraction of oil and gas from newly discovered reservoirs. The later development is illustrated in the deep-sea explorations in the Gulf of Mexico and Artic that has pushed technology to the limits and necessitates the increase of recovery rates beyond the current rate of 30 %. Understanding the movement of injected water and hydrocarbons within the reservoir via simulations incorporating field data has been key for increasing recovery rates. Electromagnetic techniques have attracted in the last decade significant attention in the oil and gas industry for its ability to overcome some of the shortcomings of seismic techniques (such as mapping of reservoirs beneath salt layers), and also because it is applicable in areas where governmental regulations forbid the employment of seismic equipment [1], [2]. While resistivity well logging has long been a standard method for determining hydrocarbon reservoirs when drilling for oil, controlled-source electromagnetic methods and crosswell electromagnetic tomography have been at the forefront of the advancement of electromagnetic techniques following the increasing computational resources and advances in technology. Controlled source electromagnetic (CSEM) [3] surveying arose from academic studies of the oceanic lithosphere in the 1980s but has initially attracted limited...