Microfacies Analysis and Reservoir Characterisation of Late Cenomanian to Early Turonian Mishrif Reservoirs, Garraf Field, Iraq

摘要

Garraf field is situated in southern Iraq, in Thi Qar Governorate. It was discovered in 1984, and proven to have hydrocarbon accumulation in Middle and Lower Mishrif by exploration and appraisals wells in Garraf. It has low relief gentle anticlinal structure aligned in NW-SE direction and has a dimension of 10km in width x 31 km in length. The Mishrif Formation were deposited in Mesopotamian Basin during the late Cenomanian to Early Turonian. Mishrif is a limestones formation with the approximate thickness of 200m. Mishrif Formation is the major reservoir and contributes almost 70% of the field's total STOIIP. For the field development plan, a 3D subsurface model was developed for resource assessment and production prediction. However, due to limited wells availability in Garraf, the main challenges are modelling the reservoir continuity and heterogeneity throughout the field to ensure the resulted model represent the actual Mishrif Formation. For the last few years the understanding on the reservoirs were solely based on the regional information, however with the recently acquired conventional core from Mishrif formation and the availability of acoustic impedance from 3D seismic data give an opportunity to investigate the reservoirs in more details. Information on the depositional environment and the facies distribution are very crucial during the facies and petrophysical modeling stages to ensure the resulted 3D model represent the actual subsurface condition. The objectives of this exercise are to integrate all the information and develop the depositional model and characterise the Mishrif reservoirs.