Integration of facies architecture, ooid granulometry and morphology for prediction of reservoir quality, Lower Triassic Khuff Formation, Saudi Arabia

Feldspar dissolution is a common feature in clastic rock reservoirs of petroliferous basins and has an important influence on reservoir quality. However, the effect of feldspar dissolution on reservoir quality varies under different depositional environments and diagenetic systems. The study area in this paper is located in the Baikouquan Formation in the northwestern margin of the Junggar Basin, which is significantly influenced by feldspar dissolution. Based on the analyses of core and thin section observations, QEMSEM, XRD, SEM, CL, fluorescence, and image analysis software combined with logging and physical property data, this study shows that feldspar dissolution in the subaqueous distributary channel of a fan delta plain, which has good original physical properties and low mud contents, significantly improves the properties of the reservoir. The main reasons for this are as follows: (1) the sedimentary facies with good original properties and low mud content is a relatively open system in the burial stage. The acidic fluids needed for feldspar dissolution are mostly derived from organic acids associated with the source rocks and migrate to the good-permeability area of the reservoir; (2) the by-products of feldspar dissolution, such as authigenic clay minerals and authigenic quartz, are transported by pore water in a relatively open diagenetic system and then precipitated in a relatively closed diagenetic system; and (3) the clay minerals produced by feldspar dissolution in different diagenetic environments and diagenetic stages have different effects on the reservoir. When the kaolinite content is less than 3%, the illite content is less than 4%, and the chlorite content is less than 12%, the clay minerals have a positive effect on the porosity. These clay minerals can reduce porosity and block pore throats when their contents are larger than these values.

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Characterization and significance of dedolomite in Wadi Nisah, central Saudi Arabia

GeoArabia ◽

10.2113/geoarabia120315 ◽

2007 ◽

Vol 12 (3) ◽

pp. 15-30 ◽

Cited By ~ 2

Author(s):

Dave L. Cantrell ◽

Abdullah Al-Khammash ◽

Peter D. Jenden

Keyword(s):

Saudi Arabia ◽

Isotopic Composition ◽

Oxygen Isotope ◽

Carbon Isotope ◽

Carbon Isotopes ◽

Reservoir Quality ◽

Meteoric Diagenesis ◽

Different Types ◽

Lower Oxygen ◽

Lower Carbon

ABSTRACT Two different types of calcified dolomite, or dedolomite, occur as stratiform and non-stratiform bodies within the Jurassic (Kimmeridgian) upper Jubaila Formation in the Wadi Nisah area of central Saudi Arabia. In the stratigraphically-equivalent subsurface Arab-D reservoir in eastern Saudi Arabia, two types of dolomite, stratiform and non-stratiform, occur which appear to be similar in architecture to the dedolomites examined in this study. However, Wadi Nisah dedolomites exhibit systematic changes in texture and isotopic composition from their precursor dolomites. Non-stratiform dedolomite contains lower oxygen isotope (average δ18O = -10.99‰) and much lower carbon isotope (average δ13C = -7.51‰) values and is much more coarsely crystalline than typical subsurface Arab-D non-stratiform dolomite; in contrast, Wadi Nisah stratiform dedolomite contains similar oxygen isotope values (δ18O = -2.89‰) and only slightly lower carbon isotopes (δ13C = 0.98‰) relative to subsurface Arab-D stratiform dolomites. We suggest that non-stratiform dolomite was more susceptible to late meteoric diagenesis than the horizontally bedded stratiform dolomite intervals. Such differences in character highlight the importance of structural and diagenetic architecture in determining later, post-dolomitization diagenesis and ultimately final reservoir quality.

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Paleozoic Clastic Systems, Reservoir Quality, and Play Mapping in the Rub’ Al Khali Basin, Kingdom of Saudi Arabia

10.3997/2214-4609-pdb.248.029 ◽

2010 ◽

Author(s):

Michael Hulver ◽

Abdul-Hameed Azzouni ◽

Craig Harvey

Keyword(s):

Saudi Arabia ◽

Reservoir Quality ◽

Kingdom Of Saudi Arabia

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Facies architecture and across-shelf variability of an extensive Lower Triassic (Smithian) microbial carbonate mound complex in the western U.S.

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/j.palaeo.2019.02.007 ◽

2019 ◽

Vol 521 ◽

pp. 42-56 ◽

Cited By ~ 1

Author(s):

Brad M. Jeffrey ◽

Maya Elrick ◽

Viorel Atudorei ◽

Spencer G. Lucas

Keyword(s):

Lower Triassic ◽

Carbonate Mound ◽

Facies Architecture ◽

Microbial Carbonate

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Geology and Production Significance of Dolomite, Arab-D Reservoir, Ghawar Field, Saudi Arabia

GeoArabia ◽

10.2113/geoarabia060145 ◽

2001 ◽

Vol 6 (1) ◽

pp. 45-60 ◽

Cited By ~ 5

Author(s):

David L. Cantrell ◽

Peter K. Swart ◽

Robertson C. Handford ◽

Christopher G. Kendall ◽

Hildegard Westphal

Keyword(s):

Saudi Arabia ◽

Quantitative Analysis ◽

Oxygen Isotope ◽

High Flow ◽

High Oxygen ◽

Reservoir Quality ◽

Low Oxygen ◽

Structural Element ◽

Log Data Analysis ◽

Ghawar Field

ABSTRACT At least five distinct types of dolomite occur in the Arab-D Reservoir in Ghawar field, Saudi Arabia – one of which appears to be responsible for high flow or ‘super-k’. These dolomite types are distinct petrographically, geochemically and stratigraphically: a finely-crystalline non-fabric-preserving (NFP) variety of dolomite in the lower Arab-D (Zone 3) with low oxygen isotope values and generally poor reservoir quality;a medium-crystalline NFP dolomite with high oxygen isotope values and very poor reservoir quality in the upper Arab-D (Zone 2);a medium to coarsely-crystalline NFP dolomite with low oxygen isotopic values and very good reservoir quality (‘super-k’) occurring in Zone 2; anda finely-crystalline fabric-preserving (FP) dolomite in the uppermost Arab-D (Zone 1) that contains high oxygen isotope values and has generally fair to poor reservoir quality. Previous studies have documented a rare fifth type of dolomite, baroque or ‘saddle’ dolomite, that occurs locally in the reservoir as well. This study also quantified and mapped the abundance and distribution of dolomite across the field, using all available core and log data. Analysis of dolomite distribution map patterns reveals that dolomite occurs in Ghawar as a series of linear trends extending for tens’s of kilometers. These map pattern trends are best-developed in Zone 2B, but are also visible in Zones 2A and 3A as well. Baroque dolomite appears to be limited to a few areas of vertically pervasive dolomite occurring on the same trends of high dolomite content. The linearity of these dolomite trends strongly suggests that some structural element is responsible for controlling their orientation. We interpret these linear patterns to have formed in response to a series of fracturing and/or faulting events that allowed dolomitizing fluids to move up into the reservoir from below, and preferentially dolomitize there. Both a qualitative and a quantitative analysis of performance data (flowmeters) in southern Ghawar (Haradh) indicate that these trends of high dolomite have a profound influence on fluid flow in the reservoir. A qualitative analysis of occurrences of ‘super-k’ in the Arab-D in Haradh suggests that most ‘super-k’ zones (seen as ‘spikes’ or step profiles on the flowmeter) occur in the high dolomite trend in Haradh. A quantitative analysis of flowmeter data and a comparison of this analysis with dolomite map patterns indicate that most reservoir flow occurs where dolomite is abundant, and suggests that there is a direct relationship between patterns of high flow and high dolomite.

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