Geological Modeling of Makhul Formation in Minagish Field: Integrating Sedimentological, Petrophysical, Geophysical and Well Test Data: An Example of Tight and Complex Reservoir from Kuwait

Alammar, Heyam M.¹; Manowar, Ahmad ²; Nikhil, Banik ³; Alowihan, Hanan ⁴; Tanoli, Saifullah ⁵; Khan, Badruzzaman ⁶; Mushnuri, Sudhakar Rao ⁷; Alvarez, Marco ⁸
(1)Exploration, Kuwait Oil Company, Ahmadi, Kuwait. (2) Exploration, KOC, Ahmadi, Kuwait. (3) Exploration, KOC, Ahmadi, Kuwait. (4) Exploration, KOC, Ahmadi, Kuwait. (5) Exploration, KOC, Ahmadi, Kuwait. (6) Exploration, KOC, Ahmadi, Kuwait. (7) Exploration, KOC, Ahmadi, Kuwait. (8) Exploration, KOC, Ahmadi, Kuwait.

The Berriasian Makhul Formation represents onset of open marine carbonate deposition overlying late Jurassic Gotnia and Hith evaporites in Kuwait. The formation varies from 400’ to 900' in thickness, generally thickening towards northeast. The lowermost part of the Makhul has been established as a source rock for the Lower Cretaceous Petroleum system. The middle and upper part of Makhul records numerous oil and gas shows during drilling, however, the reservoir was earlier considered too tight to be explored. Acquisition of core data, drilling and testing of wells MN-A, MN-B and MN-C, led to reassess the potential of this unit as a reservoir in Minagish Field.

Detailed sedimentology and stratigraphy of this formation show that Makhul can be broadly divided in three main Zones, with a change from wackestone-packestone to mudstone toward NE. Lower Makhul consists of heavily bioturbated argillaceous lime mudstone and shale. Middle Makhul contains mostly argillaceous lime mudstone interbedded with turbiditic very fine grainy lime mudstone-wackestone, finally, upper Makhul is composed of bioturbated to intensively bioturbated very fine grainy lime mudstone-wackestone interbedded which is at times slightly dolomitized. These facies suggest depositional environments ranging from Outer ramp to Middle-Outer ramp to Outer-Middle ramp setting for lower, middle and upper Makhul, respectively.

Stratigraphically, the lower Makhul is described by an asymmetric base level fall cycle. Both, lower and middle Makhul are described by complete base level asymmetric cycles. These complete cycles are described by a lower base level fall hemicycle larger than the capping base level rise hemicycle. Stepping pattern analysis shows that middle Makhul steps seaward with respect to lower Makhul and upper Makhul with respect to middle Makhul suggests a clear landward stepping pattern, signifying the upper Makhul had deeper water and lower energy deposition than the middle Makhul. Stepping patterns toward shallower conditions favor deposition of cleaner limestone in the middle Makhul, and contrast with reservoir quality of the upper Makhul. Stratigraphic concepts helped to establish rock typing and associated quantitative log clustering and layering strategy. Thus, conceptual development plan and reduction of exploratory cycle are achieved thanks to facies distribution and delineation of carbonate bodies and their consequent feedback on 3D static and dynamic modeling.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.