Three Successful Large-scale Field Tests of Crosshole Electromagnetic Tomography Technology

Abstract

Abstract A leading edge for the applied technological development of geophysics today—crosshole electromagnetic (EM) tomography technology, is an extremely challenging research topic. Its principal technological objective is to realize the direct measurement of the interwell resistivity in order to offer a two-dimensional, even three-dimensional resistivity image reflecting formation structure, reservoir property and the distribution of oil, gas and water between wells. So it not only is a momentous development of the conventional logging technology, but also will revolutionize the reservoir research. Shengli Oilfield (or SPAB) has cooperated with EMI to conduct the application study of the crosshole EM tomography technology for many years. Recently five large-scale industrial tests of the crosshole electromagnetic tomography were conducted successfully in three pairs of wells in Gudao and Chengdong oilfields attached to Shengli Oilfield. The desired results are achieved in three tests. Not only the stability and reliability of the instrument performance are proven, but also it is the first time in the world that a complete measurement data with good repeatability and high accuracy has been obtained when the interwell distance is up to 433.6 m for openhole to openhole and 147.19m for openhole to steel-cased hole. The resistivity image obtained from the inversion has provided a good geological result in analyzing the interwell hydrocarbon and sand body distribution. These achievements indicate that great progress has been made in the industrialization of the crosshole EM tomography technology. Introduction Crosshole electromagnetic (EM) tomography, an important method to reservoir research, is a leading edge technology for the applied technological development of geophysics today and also an extremely challenging and significant research topic. The frequency employed ranges from 10Hz to 10kHz. The rock conductivity of the interwell formation is measured with comparatively high accuracy and resolution, and then a 2-D or 3-D image of interwell resistivity distribution is obtained through the inversion of logged data. This technology can be applied to the study of formation structural configuration, reservoir distribution and fracture development direction of the oil deposit between wells. It can also be used to characterize hydrocarbon-enriched zones and interwell fluid distribution, monitor oil field production performance and indicate the sweep front and direction of the water, steam and polymer flooding. Thereby the success ratio of drilling high-efficiency wells in the progressive exploration and development plan adjustment of the oil field may be increased substantially. The development plan will be optimized and the ultimate recovery rate will be boosted.