The Middle Minagish (Minagish Oolite) of Berriasian-Valanginian age is oil bearing carbonate reservoir in the Minagish, Umm-Gudair and Burgan fields in Kuwait. This Formation was deposited in an overall eastward-prograding carbonate ramp setting. Spatial variation of lithofacies and reservoir quality such as porosity, permeability and saturation are mainly due to changes in the interplay of deposition, sedimentation and diagenesis within them. The challenge here is to establish a new play concept to ascertain the geometry & nature of reservoir properties in relation to depositional lithofacies in South-East Kuwait. In this study, a systematic approach has been adopted to integrate sedimentology, petrography, petrophysics, sequence stratigaphy and seismic amplitude & attributes to understand reservoir quality and distribution vis-a-vis depositional environment. Ten lithofacies were envisaged from core and petrophysical analysis, out of which peloidal, bioclastic and oolitic grainstone and packstone have good reservoir quality with intraparticle and moldic pores as well as good permeability. A 3rd order Sequence stratigraphic framework was constructed incorporating well and seismic data to identify genetically related reservoir facies and its distribution. A package of forced regression shoal facies is recognized where inner ramp coarse grainstone overlies outer ramp bioturbated pack/wackestone. Seismic amplitude anomaly and waveform facies classification was used to identify lateral facies distribution constrained with conceptual depositional model. 2D seismic inversion was judiciously used to visualize the geometry and spatial distribution of reservoir facies and a new play concept towards north beyond the area of field development. Locally developed shoal in inner ramp and patch reef & reworked carbonate were found to be good locales for porosity development and preservation. The sequence stratigraphic framework shows lateral continuity and cycle of vertical heterogeneity of reservoir architectures. These led to a new play concept of strati-structural play of Minagish Formation towards deep basinal part to the north of SE Kuwait. Introduction: The Minagish Oolite is the primary reservoir in the Minagish Field and significant contributor in Umm Gudair and Burgan Fields. The Minagish Oolite, which is Berriasian-Valanginian in age, is the Middle member of the Minagish Formation (Figure-1). The Minagish Oolite/ Middle Minagish are equivalent to the Ratawi Oolite of the nearby Wafra Field and the Yamama Formation of Southern Iraq. Ten lithofacies were envisaged from core and petrophysical analysis, out of which peloidal, bioclastic and oolitic grainstone and packstone have good reservoir quality with intraparticle and moldic pores as well as good permeability. The most important lithofacies are peloidal wackestones-grainstones, Oolitic grainstones and bioclastic wackestones which together form = 85% of the reservoir. Middle Minagish was deposited on a broad, prograding carbonate ramp. It was deposited within a single third order, sea level cycle, composed of stacked, broadly coarsening upward fourth or fifth order cycles. Lithofacies and Depostional environment: The Minagish Formation is devided into upper and lower dense members characterized by relatively tight lime mudstones and wackestones separated by middle bioclastic Oolitic grainstone member. A detail core study of Minagish Formation was carried out in Minagish, Umm Gudair, Burgan and khasman fields. Ten lithofacies were identified based on core studies which are given below with corresponding sedimentary structure and depositional environment.
The Lower Cretaceous Minagish Formation forms one of the most prolific oil reservoirs in onshore Kuwait, with key reservoir units located in thick oolitic grainstones forming the lower half of the Middle Minagish Member. Within the central and eastern part of Kuwait, the upper part of the Middle Minagish consists of inner ramp skeletal packstones, that are variably cemented, for which the reservoir potential is poor. Following exploration campaigns carried out by KOC in the unexplored south-western area of Kuwait, unusual oil staining has been observed in the uppermost part of the Middle Minagish Member highlighting a potential new hydrocarbon play. As part of a multiwell study investigating the Middle and lowermost Upper Minagish Members cored in south-western Kuwait, this work focuses on understanding the occurrence of hydrocarbon stained deposits within the uppermost Middle Minagish and assesses their extent. The study aims to characterise the sedimentological make-up and analyse the field-scale depositional organisation to assist in the prediction of reservoir architecture. A facies analysis has been carried out and has resulted in the interpretation of the depositional environments. The key surfaces characterised in core along with openhole log data have helped in the interpretation of a sequence stratigraphic framework across both the reservoir and non-reservoir units. The facies analysis and vertical facies evolution across the cored Minagish succession suggest deposition in an intertidal to marginal/proximal mid-ramp setting, with the development of oolitic geobodies both in a marginal shoal corridor and sand bars formed in a more landward position on the inner ramp. The more proximal sand bars are typically recorded in the south-west Kuwait area and are not present further towards the east (e.g. Minagish and Umm Gudair Fields; Davies et al., 2000; Davies et al., 2001). The vertical depositional organisation indicates that the Middle Minagish is part of a large-scale regressive trend, characterised by the upward evolution from marginal inner ramp/proximal mid-ramp oolitic grainstones to skeletal packstones terminating with deposition of internal oolitic/carbonate sand bar to locally intertidal deposits. Hydrocarbon staining is observed where internal oolitic/carbonate sand bar/intertidal deposits are capped by key surfaces, locally associated with dissolved cavities suggesting exposure. These surfaces are interpreted as a sequence boundary above which a distinct change in deposition from clean carbonates to clay/organic matter-prone deposits (Upper Minagish) occur. The well correlation highlights a condensation of the sand bar/intertidal deposits in the south-western part of the study area, which is a result of a progressive decrease in accommodation at the end of the regression that is amplified in the landward position of the system. The work has been carried out prior to the establishment of the reservoir architecture and has helped in the prediction of rock type distribution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.