Lower Najmah Shale: An Emerging Shale Resource Exploration Target in Kuwait
Late Jurassic Najmah and Sargelu formations are established naturally fractured unconventional reservoirs in Kuwait which are currently being explored and developed together by conventional methods. Focused study on the lower organic rich unit of Najmah Formation of Oxfordian age (Lower Najmah Shale) has brought out its potential as shale gas and oil play. A paradigm shift in exploration and exploitation strategy for these resources is vital for unlocking the resource potential. The Lower Najmah Shale has been synergistically evaluated in terms of depositional environments, source facies richness, distribution, thickness and maturity, mineralogy, pore pressures and natural fractures to locate potential thrust areas for exploration and exploitation. Lower Najmah shale is subdivided into three distinct units designated as lower, middle and upper. The lower and upper units comprise dominantly organically rich bituminous calcareous mudstone facies deposited in an outer ramp to basinal environment. The middle unit comprises predominantly wackestone-packstones deposited in a proximal to distal outer ramp setting. Source richness analysis indicates total organic carbon to vary from 1.95 to 14.5% with higher content in the northern part of Kuwait. Isopach of the unit indicates thickness increase towards south Kuwait. Isolith map for the bituminous calcareous mudstone shows development of two thick maxima's centered in northeastern and southern parts of Kuwait. Source maturity indicates the northwestern part of Kuwait to lie in the late maturity oil-wet gas window while rest of the areas occur in the middle to late maturity oil window. An average porosity of 5-6% and high hydrocarbon saturations have been interpreted. The mineralogy is dominated by calcite with minor amount of clay, dolomite, pyrite and quartz. The unit is over pressured at 0.80-0.92 psi/ft and fractured with dominant fracture trend being NE-SW and NW-SE. Fractures oriented NE-SW aligned with the present day maximum stress are open contributing to production. Basin model studies indicate substantial in place resource potential to exist in this play. The study has indicated that the northern part of Kuwait has good potential for exploration of shale gas while the southern part is prospective for shale oil resources. Drilling of horizontal multilateral wells, multistage hydraulic fracturing and innovative well completions are key to unlock the potential of this unconventional resource play.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014