In Situ Formation of Petroleum in Oolites‐ Ii: A Case Study of the Arab Formation Oolite Reservoirs

Abstract

In Part I, (Journ. Petrol. Geol. 7 (3) 267–276) a scheme for the in situ generation and accumulation of hydrocarbons was presented. It was concluded that the indigenous origin of petroleum in oolites, which preculdes a long and wasteful primary migration process, affords another explanation for the exceptionally rich petroleum accumulations which characterise oolite reservoirs. The present paper now tests the validity of that proposal by a selected case study. For an unequivocal discussion of an oolite reservoir productive of petroleum generated in situ, it would be necessary to describe in some detail those formations either underlying, overlying or lateral to the formation of interest which, because of their hydrocarbon content in the general region, might perhaps be supposed to have been the original source of the petroleum now found in the oolites. such an account would be more detailed than space permits. The need arises, therefore, for the selection of an example which allows the least number of alternative possibilities. This was the guiding principle behind the choice of the prolific Arab Formation (Upper Jurassic) of Saudi Arabia as a case study (Fig. 1)

Dissolution of ooids in seawater‐derived fluids – an example from Lower Permian re‐sedimented carbonates, West Texas, USA

“…Given their deposition in close proximity to sea level and their metastable mineralogy, ooids are prone to early diagenetic alterations, and studies can provide valuable clues about the overall geological history of the strata Harris, 2019). In addition, oolitic carbonates also commonly form large hydrocarbon reservoirs and comprise a significant share of global carbonate reserves (Moore & Druckman, 1981;Harris, 1984;Ibe, 1985;Burchette et al, 1990;Lehrmann et al, 2012).…”

Geochemistry and nature of organic matter of the Pleistocene—Holocene carbonate‐evaporite sediments of Al‐Khiran, Southeastern Kuwait

“…This became generally accepted, given that ooids are internally composed of layers of organic mucilage alternating with concentric carbonate-rich laminae (Shearman, 1965;Shearman et al, 1970). A number of studies related to the identification of the amount and character of organic matter in ooids have been made in the ancient carbonate sequences of the Arabian Gulf Basin (Ibe, 1984(Ibe, , 1985Abdullah & Kinghorn, 1996). Other geochemical investigations have concentrated on Holocene carbonate sediments as modern analogues for understanding the nature and preservation of organic matter in their ancient equivalents (Ferguson & Ibe, 1982;Ibe, 1983;Ferguson, 1987;Kenig et al, 1990).…”