--> Abstract: The Multi-Transient Electromagnetic Method, Deep Subsurface Hydrocarbon Mapping from Surface Acquisition Both Onshore and in Shallow Water. A Case Study from Onshore Trinidad, by Jason Robinson, Bruce Walker, Joseph R. Lach, and Ed Morris; #90078 (2008)
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The Multi-Transient Previous HitElectromagneticNext Hit Method, Deep Subsurface Hydrocarbon Mapping from Surface Acquisition Both Onshore and in Shallow Water. A Case Study from Onshore Trinidad

Jason Robinson1, Bruce Walker2, Joseph R. Lach3, and Ed Morris4
1Petroleum Geo Services, Houston, TX
2TEN Degrees North Energy Limited, San Fernando, Trinidad and Tobago
3Knowledge Reservoir, Houston, TX
4PGS Multi-Transient EM, Edinburgh, United Kingdom

The Multi-Transient Previous HitElectromagneticNext Hit (MTEM) technique produces resistivity profiles which can enable the identification of hydrocarbons in the subsurface. MultiTransient Previous HitElectromagneticNext Hit is a novel Controlled Source Previous HitElectroMagneticNext Hit (CSEM) technique that enables deep resistivity imaging with surface acquisition - both onshore and offshore. It can be used as an adjunct to other data and methods or in some cases a complete replacement.

The MTEM method involves the injection of current into the earth from source bi-pole, and the measurement of the resultant electric field using a spread of receiver bi-poles. The data is then processed and inverted to deliver resistivity sections that delineate subsurface resistors which can be interpreted as hydrocarbon bearing strata. The basic method, survey design, field operations, processing and inversion are described.

A case study is shown where MTEM, an Previous HitelectromagneticTop surveying technique, is used onshore Trinidad. The prospect terrain comprises low-lying hills covered by dense tropical forest, and the subsurface is faulted and fractured. Thus, seismic often gives poor results and can be costly. The project objective was to image stacked reservoir sands at depths between 150 and 1500m.

Excellent data quality was achieved, the thrust and reservoir are clearly visible in all sections. The faults ties with surface locations confirmed with surface geology mapping. Prospective pools in this area appear as resistivity anomalies (>15 Ωm) that stand out from the background resistivity (1-3 Ωm).

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas