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Lithofacies, Diagenesis and Depositional Sequence; Arab-D Member, Ghawar Field, Saudi Arabia

By
J. C. Mitchell
J. C. Mitchell
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P. J. Lehmann
P. J. Lehmann
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D. L. Cantrell
D. L. Cantrell
1
Exxon Production Research Company Houston, Texas 77001
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I. A. Al-Jallal
I. A. Al-Jallal
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M. A. R. Al-Thagafy
M. A. R. Al-Thagafy
2
Arabian American Oil Company Dhahran, Saudi Arabia
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Published:
January 01, 1988

Abstract

Ghawar, the world's largest oil field, is located in the Eastern Province of the Kingdom of Saudi Arabia. This giant field is formed by an elongate northeast to southwest trending anticline. Production comes from Arab-D Member carbonates of the Upper Jurassic Arab Formation, which consists of four geographically-widespread carbonate/evaporite members. The Arab-D comprises two major shoaling upward cycles deposited during a relative highstand in sea level. These cycles are composed of smaller scale upward shoaling cycles and are comprised of a variety of skeletal grainstones and packstones with ooid grainstones locally common in the uppermost Arab-D. The Arab-D is further subdivided into time-stratigraphic reservoir zones and subzones that are based largely on porosity log pattern correlation. The first cycle comprises Zone 3 of the Arab-D. The abundance of grain-supported textures (packstone, mud-lean packstone, and grainstone) stays fairly constant in Zone 3B, but increases upwards through Zone 3A. A second shoaling-upward cycle beginning near the base of Zone 2B resulted in the deposition of virtually mud-free shoal-water deposited sediments seen in Zone 2A and culminated in the deposition of thin subtidal to intertidal/supratidal cycles and sabkha evaporites of Zone 1 and the lower portion of the Arab-D Anhydrite. The overlying upper Arab-D Anhydrite comprises sabkha evaporites and subaqueous evaporites with thin carbonate interbeds that can be traced for hundreds of kilometers. The overall pattern of sedimentation seen at Ghawar is that of a thinning carbonate section and a thickening evaporite section going from north to south, even though the overall thickness of the Arab-D Member remains fairly constant.

The major diagenetic processes active in the Arab-D include dolomitization, leaching and recrystallization, cementation, compaction and fracturing. In general, interparticle porosity is abundant and moldic porosity is common in the reservoir, whereas intrapraticle, fracture, burrow and shelter porosity are much less common or rare. Intercrystal pores are common in dolomites. Microporosity is present throughout the reservoir in limestones and dolomites. It occurs as microporous skeletal and non-skeletal grains, microporous matrix and micropores between cement crystals.

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Contents

SEPM Core Workshop Notes

Giant Oil and Gas Fields: A Core Workshop

Anthony J. Lomando
Anthony J. Lomando
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Paul M. Harris
Paul M. Harris
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SEPM Society for Sedimentary Geology
Volume
12
ISBN electronic:
9781565761001
Publication date:
January 01, 1988

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