Класс Месторождения:
Тип Месторождения: Нефтегазовое
Местоположение:
Местность:
Стадия разработки: Добыча
Год открытия: 1956
Источник информации:
Метод открытия:
Площадь: 1608.86 км²
Hassi Messaoud Field
The Hassi Messaoud Field, a very thick sandstone reservoir of Cambrian age covering an area of 2000 km2 is a multi-billion barrel oil field in the Triassic Basin of Algeria (Fig. 1).This oil field was discovered in 1956. The producing layer, which occurs at an average depth of 3400 m, is characterized by largely variable petrophysical properties. The properties impacting productivity (including porosity, shaliness and permeability ) remain unpredictable, despite the knowledge accumulated from more than 1216 vertical and horizontal wells continuously cored over the past 48 years. Note that most of the documents used in this study concerning the Hassi Messaoud field and the Saharan platform are Sonatrach internal documents; because of this, the references are sometimes not indicated.
The geographical situation
Hassi Messaoud is located 800 km southeast of Algiers, between the meridians 5°30 6°00 and the parallels 31°00 and 32°00N (Fig. 1). It is 350km from the Algero-Tunisian frontier and 80 km east of Ourgla. It is considered to be one of the largest oil deposits in the world and the more prospected of the Saharan platform.
Figure 1: Location map of the Hassi Messaoud field, Algeria (Mc Gowen et al.,1996)
Structure and stratigraphy
The Saharan desert within the so-called Triassic Basin (Oued Mya Basin) is part of the North African stable craton. The basin has had a long history from Cambrian times onwards, and has a sedimentary column of about 5,000 m (Fig. 2).
Figure 2: Left handside: Summarized stratigraphy for the Hassi Messaoud field (Balducchiand pommier, 1971). Right handside: Detailed column of the four productive zones R3, R2, Ra, Ri of the cambrian of Hassi Messaoud field .
The Cambrian sediments are a thick series of fluvial and shallow marine sandstones, deposited on a peneplained surface composed, in the Hassi Messaoud area, of Early Cambrian granites. The Algerian Sahara was invaded by a relatively deep anoxic sea during the Ordovician, but this was followed by a regional regression and a period of coarse clastic, continental and glacial sedimentation. During the Late Silurian, deep marine conditions once again occurred over a wide area in North Africa, but the Caledonian orogeny led to the creation of a number of gentle, regional uplifts. Devonian sandstones and shales were deposited extensively in fluvial and shallow marine environments over much of North Africa, including Algeria, and lie unconformably on tilted and eroded Lower Palaeozoic sediments. They were followed by deltaic and marine sandstones and shales of Carboniferous age. It is not known for certain whether these Upper Palaeozoic sediments were deposited over the Hassi Messaoud high because they have not been preserved there. They may have been deposited with a reduced thickness, but in any case would have been subsequently removed as a result of the tectonic upheavals related to the Hercynian orogeny of Late Carboniferous to Permian times. The grain of the Hercynian orogeny in the Hassi Messaoud area is oriented mostly NE-SW, as is typically seen in the trend of the Messaoud - El Agreb (Sonarach, WEC, 1995). The productive formation of Hassi Messaoud is a series of Cambrian sandstones, with an average thickness of 300 m and 4 productive zones denominated R3, R2, Ra, Ri (from bottom to top). The Ra represents the best reservoir qualities. The Paleozoic of Hassi Messaoud has been eroded by the Hercynian unconformity which reaches the R2 in places. This erosion is increasingly important from the periphery to the center where the Ra is locally absent (Fig. 3).
Figure 3: Peel Map of Hassi Messaoud Field: Reconstruction of the hercynian unconformity distribution of underlying formations by « peeling off »the overlying formations. The red zones are the production zones of the field.
Structurally, only the top of R2 allows us to correctly define the geometry of the Cambrian of Hassi Messaoud (Fig. 4). The Hassi Messaoud structure appears as a large SSW-NNE oriented anticline, affected by the major faults SSW-NNE.
Figure 4: Hassi Messaoud Field. Isobaths of the top of the Cambrian R2 showing an anticline feature with low dipping faults.
The heterogeneity of Hassi Messaoud field (HMD) is tied to two important factors:
A. faulting and the erosion cause the local complications;
B. Diagenesis is tied to tectonics and caused the deterioration of the reservoir qualities.
The drains
In different sectors of the Hassi Messaoud field (HMD), different drains participate in the production. In the central zone it is D2, ID, D1. In the west periphery of the field it is D4 and D5 (fig. 2).
The production zones
The pressure evolution of wells according to the production has been interpreted with the help of numerical simulators. This brought out 25 producer zones parted by the unproductive zones (Fig. 5). This subdivision of the field (this zoning) is not based on geological criteria. Some producer zones are limited by the major faults which can play a major role as permeability barriers. However, the limits for other zones are inexplicable
Figure 5: Some examples of Intracambrian intrusions in the Southwest part of the Hassi Messaoud Field. Red frame enclose the area of interest. A system of 25 isolated zones having different petrophysical and pressure characteristics, can be identified within the reservoir.
Gas injector
Within the producer zones, gas injections reveal an apparent anisotropy of fluid movement. The gas injected can reach neighboring wells in differing lengths of time reaching up to 10 years.
Dry wells
The plantation of 106 dry wells in the field is considered to be one of the negative points inexplicable by the present geological and reservoir models.
Data source:Reservoir characterization and freservoir modeling in northwestern part of Hassi Messaoud field Algeria. Fadila Bessa, 2004
Следующее Месторождение: Bouhadid