Influence of the pore space structure and wettability on residual gas saturation

A significant part of hydrocarbon deposits in Russia is in the late stage of development. The distribution of residual oil and gas reserves is determined by the properties of the holding rocks. Estimating of deposits’ residual gas saturation is an important scientific task. The allocation of zones with the maximum undeveloped gas reserves will allow to select areas in long-developed fields for the intensification of production in the most efficient way. To search for such “sweet” zones, it is necessary to determine the factors that provide the value of the residual gas saturation. The reliance of the value of trapped in pores, residual gas saturation on such rock properties as pore space structure and wettability is studied in this article. The influence of formation pressure value and behaviour on making up of residual gas saturation during field development is not accounted in this work. The study of a wide collection of core sampled from productive deposits of the Orenburg oil and gas condensate field, the Vuktylskoe oil and gas condensate field, oil and gas field of Orenburg region, and also three areas in the East Caucasian petroleum province confirmed that the value of structure-trapped oil and gas saturation of carbonate and terrigenous rocks is directly proportional to the ratio of pore diameters and channels connecting them. Herewith the angular coefficient of the regression equation for this relationship for carbonate rocks directly depends on the quantitative characteristics of the predominant (relative) wettability. The obtained relationships make it possible to predict the value of residual gas saturation based on knowledge about the pore space structure and the surface properties of rocks.

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LABORATORY STUDIES OF SANDSTONE RESERVOIRS GAS DISPLACEMENT FROM HAVING STRONG WATER DRIVE

The APPEA Journal ◽

10.1071/aj73027 ◽

1974 ◽

Vol 14 (1) ◽

pp. 189 ◽

Cited By ~ 4

Author(s):

B. A. McKay

Keyword(s):

Elevated Temperatures ◽

Water Saturation ◽

Pore Space ◽

Sedimentary Basins ◽

Water Flooding ◽

Gas Saturation ◽

Gas Recovery ◽

Irreducible Water Saturation ◽

Residual Gas ◽

Residual Gas Saturation

Investigations by the Petroleum Technology Section of the Bureau of Mineral Resources have shown that a substantial residual gas saturation is trapped behind the flood front in gas-producing reservoirs having a strong water-drive; the volume of gas trapped may be as high as 44 per cent of pore space, and lies within the same range as residual oil saturation in a flooded-out oil reservoir.Core samples from gas-productive reservoirs in three Australian sedimentary basins have been subjected to laboratory tests to measure this effect. The tests comprised capillary pressure measurements, water-flooding by dynamic-displacement and imbibition at ambient and elevated temperatures, and repeat gas recovery measurements in core samples exhibiting variations in irreducible water saturation.The results show a loose correlation between porosity and residual gas behind the flood front in these samples. Temperature appears to have little effect on the residual gas saturation. Gas recovery, however, is strongly dependent on the irreducible water saturation established prior to flooding.

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Carbonate oil and gas source rocks wettability alteration due to influence of polymer-colloidal drilling mud

Proceedings of OilGasScientificResearchProjects Institute SOCAR ◽

10.5510/ogp2021si200545 ◽

2021 ◽

pp. 17-27

Author(s):

N. A. Skibitskaya ◽

◽

I. O. Burkhanova ◽

M. N. Bolshakov ◽

V. A. Kuzmin ◽

...

Keyword(s):

Surface Properties ◽

Oil And Gas ◽

Pore Space ◽

Space Structure ◽

Source Rocks ◽

Wettability Alteration ◽

Drilling Mud ◽

Rock Samples ◽

Gas Saturation ◽

Gas Source

Evaluation of rock wettability is an important task, since this parameter determines the distribution of water and oil in the reservoirs and their relative and phase permeability. The reliability of evaluation the wettability of rock samples depends on the drilling-in conditions during core sampling and core sample preparation methods. The investigation of the surface properties of the core from the Orenburg oil and gas condensate field showed that using of polymer-colloidal drilling mud leads to hydrophilization of the samples' surface. To obtain information on the actual wettability values of rock samples taken from wells drilled with polymer-colloidal drilling mud a method for estimating the relative (predominant) wettability of rocks based on petrophysical and lithological studies data is proposed. The authors suggest that the extraction of oil and gas source rock samples leads to irreversible changes in surface properties that cannot be restored. Keywords: selective wettability; relative wettability; predominant wettability; polymer-colloidal drilling mud; residual gas saturation; trapped gas saturation; pore space structure; extraction.

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