Cand. Tech.Sci. Ponomareva M.V., Blochitsyna A., Nikitina A., Ponomareva Ye.

Karaganda State Technical University. Kazakhstan

ALLOCATION OF OIL-FILLED RESERVOIRS BY A COMPLEX OF LOGGING METHODS ON AKSHABULAK DEPOSIT

Nowadays a complex of logging methods is successfully applied to locate producing horizons and collector-layers. According to results of geophysical researches with the use of geologic-geophysical programs 28 reservoirs are selected. These reservoirs are dated to J-III, J-III^a, J-II, J-I, K-II-1, K-II-2 horizons.

By the character of saturation 15 reservoirs are water-filled, 13 reservoirs are oil-filled. Akshabulak deposit is situated in Terenozek district of Kyzylorda region, Kazakhstan Republic. Reservoirs properties and variance factor are defined on the base of laboratory research of core using equal or prevailing accepted values of porosity lower limit for each horizon (K-II – 10,5%, J-I – 18%, J-II – 15,9%, J-III^a carb. – 7%, J-III^a terr. – 15%, J-III – 15% and permeability cut-off is 0,001 mcm²). Reservoirs of producing horizons are terrigenous, pore type (except J-III^a).

The reservoirs of J-III horizon are made of well-sorted slightly cemented sandstones and quartzous and quartz-feldspar sands. These rocks are slightly argillaceous, well-sustained areally, with grain`s diameter from 0.1 to 1 mm. Sandstones are usually medium-grained, more rarely large-grained, noncarbonated. The main argillaceous mineral is kaolinite, rarely illite without chlorite and montmorillonite. High concentration of quartz and low concentration of feldspar (less than 20%) and argillaceous mineral (under 5%) are observed in the lower part of sand formation of J-III horizon. In the upper part of sand formation concentration of quartz is lower (less than 70%), concentration of feldspar (more than 20%) and argillaceous minerals is higher (more than 5%). In granulometric aspect sandstones in the lower part of cut-away are sorted better (sorting coefficient less than 2), than in the upper part (sorting coefficient more than 3).

The J-IIIa horizon is made of carbonate cemented sandstones and limestones with subordinate interlayers of caclcareous sandstones, rarely gritstones. The limestones are grey, fine-grained and cryptomerus , tight, hard and massive. The rock is usually fractured. Fractures are oil-filled or made of calcite. The J-II horizon is made of fine-and medium-grained sandstone, quartz-feldspar, silty and sandy silt.

In channel field intervals the J-I horizon is made of fine-grained, well-sorted, quartz-feldspar, hard and slightly cemented sandstones passing into sands and sandy silt thickness of which more than 20 meters. In out-channel field the horizon is absolutely mudded. Horizon`s reservoirs are made of subordinate interlayers of quartz-feldspar, fine-grained and silty sand.

The K-II-1 horizon`s reservoirs are made of slightly cemented sandstones and inequigranular sands with gravel inclusion.

The K-II-2 horizon`s reservoirs are made of interlayering sandstones passing into sands and silts. Tight argillaceous-carbonate cemented gravel`s layers are spread in the lower part of reservoirs. In the upper part of horizon reservoirs are made of fine-and medium-grained, quartz-feldspar sandstones passing into medium-grained and carbonate-argillaceous cemented sandstones and sands. Inequigranular sandstones and sands with gravel inclusion are prevailing in the middle and lower parts. The basement of reservoirs consists of carbonate cemented gravelites.

According on results of core analysis permeability of the J-III horizon`s reservoir formation varies from 0,001 to 25,5 ìcì² and its porosity changes from 15 to 32%.

Sand reservoirs of J-III^a horizon (carbonateness less than 30%) are defined by core with porosity from 15 to 32%, permeability 0,853 ìcì². Porosity of carbonate reservoirs (carbonateness more than 30%) varies from 7 to 13%.
Permeability 0,3·10^-3 ìcì². Core porosity of J-II horizon`s is 15 – 22 %, permeability changes from 0,001·10^-3 äî 0,32·10^-3 ìcì² (average value 22% and 0,22·10^-3 ìcì²).

Core porosity of J-I horizon`s changes from 18 to 32% , permeability usually is from 1 to 3150 mD (average value 1360 mD). Core porosity of M-II horizon varies from 15 to 30.5%, permeability is from 0.1 to 7000 mD. The results of complex interpretation is given below.

	ARGILLA		SILTSTONE		CARBONACEOUS VARIETIES
	SANDSTONE		TIGHT SANDSTONE		FREE WATER
	SILTY SANDSTONE		PUDDING ROCK		HYDROCARBONS

The results of complex interpretation