Класс Месторождения:
Тип Месторождения: Нефтегазовое
Местоположение:
Местность:
Стадия разработки: Добыча
Год открытия: 1944
Источник информации:
Метод открытия:
Площадь: 3.28 км²
Kirmaku Oil Field is located in the central part of the Apsheron Peninsula, 15 km north of Baku, and between two large oil-bearing regions: the Balakhany-Sabunchi-Ramany group of oil fields to the southeast and the Binagady-Chakhnaglyar-Sulutepe group of oil fields to the southwest.
Three topographic features are distinguished in the area of Kirmaku Field: the Kirmaku Ridge, Binagady Height, and Bogboga Mud Volcano.
The highest point is Kirmaku Mountain (104.7 m) located in the southern part of the Kirmaku Ridge. The surface of the mountain is covered with many tar pits and shallow wells, which produced oil in the past.
Structurally, Kirmaku Field has an asymmetric, box-like shape (Figures 1, 2). Dips are 40–50° on the eastern flank, and 60–70° on the western flank; dips decrease to 25° toward the crest, and on the periphery of the structure they decrease to 10°. The axis of structure extends about 3 km, and the width of the structure is about 400 m. The core consists of Paleogene and Neogene rocks.
Figure 1. Geologic map of Kirmaku Oil Field (Modified after Alibekov et al., 1964). 1—Lower Balakhany Suite, 2—“Pereryv” Suite, 3—NKG Suite, 4—NKP Suite, 5—KS Suite, 6—PK Suite, 7—Pontian Stage.
The Kirmaku structure is made up of the Neogene rocks (Productive Series of Middle Pliocene and Pontian Stage of Lower Pliocene). The crest consists of Pontian shale surrounded by the Podkirmaku Suite of the Lower Productive Series. The structure consists mainly of the Kirmaku Suite deposits characterized by a frequent alternation of shale, silt and sand. Recent and old Caspian Sea deposits rest unconformably on older Neogene rocks exposed by erosion.
In the 1950s, 62 exploratory wells were drilled in three phases within the field area (Figures 1,2). Most of the wells were cored, and a total of 1,039 core samples were recovered and analyzed.
Figure 2. Structural map and cross-section of Kirmaku Oil Field (Modified after Alibekov et al., 1964). (a) Structural map on the top of Pontian Stage: 1—well, 2—contour line on top of Pontian, 3—outcrops of Pontian rocks; (b) cross-section.
The major productive interval, the Kirmaku Suite (KS), is represented by alternating shale, very fine- to fine-grained, argillaceous sand, and silt of brown and gray color. Total thickness of the suite ranges from 250 to 260 m. The KS interval is the most consistent in thickness and lithology over the whole section of the Productive Series.
Quantitatively, sand and silt content prevail over that of shale. The KS section consists of 74% sand, sandstone and silt, and of 26% shale and sandy-silty shale. Thickness of sand and shale beds varies between 1–2 mm to 10–20 cm. Among sandy-shaly alternations one can observe thicker interbeds of sand and shale up to 3–4 m. The number and thickness of sandy-silty beds are higher in the lower portion of the section. Average porosity of reservoir rocks is 26%, and the carbonate
cement content is 8–16%.
The underlying Podkirmaku Suite (PK) is the second oil-bearing formation penetrated by boreholes both in the crestal area of the structure and on its flanks. The PK Suite is the thickest (about 40 m) in the southern plunged portion of the structure. Toward the crest, thickness decreases significantly. The PK section is made up of medium- to coarse-grained quartz sand with large quartz grains and unevenly shaped pebbles. Sand is gray and light-gray in color, whereas pebbles are black. The upper part of the PK section contains mediumand fine-grained sand with some thin shale interbeds. In the lower and middle parts, grain size increases and shale interbeds disappear. Within the PK section, particularly in the lower part, one can observe interbeds of very dense and hard calcareous sandstone. Thickness of this sandstone ranges from 10–20 cm to 50 cm. Average porosity of the reservoir rocks is 26–28%; carbonate cement content is 12–15%.
Kirmaku Oil Field has long been known as the place of oldest production of oil and asphalt. The precise date of earliest Kirmaku Oil Field production is unknown, but accounts date back as early as 1834.
Initially, oil was produced from shallow pits in outcrops using bailers. Later, shallow wells with timber-lined walls were dug. These wells were situated, mainly, on the eastern and southern slopes of Kirmaku Mountain, and to a considerably lower extent, on the western slope. Depending on the location within the area and on the depth of productive formation, well depth varied greatly. Average depth was 50–60 m; however, some were up to 190 m deep. Some wells were very shallow: no more than 10–20 m deep.
In the past, Kirmaku Field oil and gas wells were produced at maximum rates with rapid reservoir depletion. In some cases, flow per well reached 11–13 tpd (80–90 bpd). Production rate, however, could be sustained only for 1–2 months, and then declined to 1.0–1.5 tpd.
Such practice, at that time, was believed to be normal, and most wells typically produced for several months and sometimes even for years.
As production rate declined, wells were deepened to the next productive bed.
Peak monthly oil production reached 4,500–5,000 tons before 1914 and World War I. The total number of wells (in and out of operation) reached 1,500. About 50 of them (the most productive) were operated until 1926. Digging of new wells was stopped in 1913, and was prohibited from then on. Maximum potential production rate was 3–5 m3/day and was based on well tests. The longest oil column encountered during well testing was 60–70 m at a depth interval of 100–120 m.
In other wells, the length of oil column was smaller and, in some cases, wells were dry. As a rule, the wells produced no water. Water first appeared in 1914–1917 at the northern part of the eastern flank.
Oil was characterized by the following properties: density = 0.958–0.988 g/cm3, Engler viscosity at 45°C = 10–16. A lighter oil with density of 0.903 g/cm3 and Engler viscosity of 6.84 was produced in Well 41 from a depth of 90–101 m.
At present, Kirmaku Oil Field is virtually depleted of moveable oil and should be considered as a deposit of bituminous sands.
Field development by routine well drilling probably will be quite ineffective. The use of one of the enhanced oil recovery methods (e.g., heat stimulation or injection of solvents) probably will not be effective, because the oil-saturated rocks are penetrated by many wells which will be very hard and expensive to seal.
Field development by mining appears to be a reasonable one. However, considering that the area has been produced for a long period of time, the advantage of this method should be verified by digging at least one experimental, sloped tunnel (with a drilling chamber) at the base of productive formation, for drilling updip boreholes.
Pilot horizontal wells (164, 72, and 187-m long) were drilled at the base of the southern slope of Kirmaku Mountain in 1956. The wells were drilled using water as a drilling fluid, and completed without casing. This project demonstrated a real possibility of producing oil from such wells. At the maximum penetration into productive formation (2.0 m), one of the flowing wells has been producing at approximately 5 m3/day of total liquids including 40–60 kg of oil per day. Initial production was 10–11 m3/day of total liquids and 80–110 kg of oil per day.
Using geological, analytical, and field data, one can conclude that drilling horizontal wells from the ground level is the most reasonable technique for secondary development of bituminous sands of Kirmaku Oil Field. The advantage of this technique is due to: (1) absence of thick overburden, (2) absence of large volumes of liquids, (3) possibility for development of bituminous sands, and (4) presence of highlydeveloped infrastructure.
Data source: Petroleum Geology of the South Caspian Basin Leonid A. Buryakovsky, George V. Chilingar, Fred Aminzadeh. 2001
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