Oil Below Oil-Water Contacts: Implications on the Structural Evolution of Minagish Oolite Reservoir, Minagish Oil Field, Kuwait

Muhammad W. Ibrahim* and Tahir El Gezeery
KOC
*[email protected]

A study of the structural evolution of the Minagish oil field revealed that the trapping structure began in Early Cretaceous time as a minor dome at the SSE flank of a NW-trending Jurassic anticline. The Minagish anticline assumed the present-day motif by Maastrichtian time, gently tilted towards the NNE and was dissected by an E-W fault during Tertiary times. The fault separated two main compartments of the Minagish Oolite reservoir: an up-thrown symmetrical northern sector, and a wrenched and down-thrown asymmetrical southern sector. The incipient Minagish structure affected the thickness and deposition of the oolitic facies of the Minagish Oolite. Subsequent regional NNE tilts had a minor effect on shifting the position of superior oolitic facies in relation to present-day structural peaks of the Minagish Oolite reservoir. However, Tertiary differential displacement of the two main compartments influenced the thickness and position of the occluded tarmat layers, and preserved a record of Tertiary oil/water contacts. The structural evolution of the Minagish Oolite explains the preservation of sealing tarmats within superior oil-bearing reservoir facies above and below the present-day oil/water contact in the northern sector, and the preservation of tarmats within the relatively inferior and water-bearing facies below present-day oil/water contact in the southern sector of the Minagish Oolite reservoir. Hence, technically there appears to be producible oil sealed by tarmats below the present-day oil/water contact in the northern sector of the Minagish Oolite reservoir of Minagish oil field.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain