User:VandenbosTyler/Temsah Gas Field

Location

The Temsah gas field is located offshore in the northeastern section of the Nile Delta, between latitudes 31° 46’ & 31° 52′ N and longitudes 32° 07’ & 32° 13’ E; which is about 65 km to the northwest of Port Said. The Temsah Gas Field has a surface area of approximately 1155 km² which includes the Temsah and Denise fields. The Temsah Gas Field resides in the Nile Delta Basin and it is considered the most prolific province for gas production in Egypt. The Nile Delta Basin is located in the eastern Mediterranean area and covers a surface area of around 250,000 km². The Nile Delta Basin has three sub-basins; eastern, central and western. The eastern and western sub-basins are prospective areas for hydrocarbon source and reservoir rocks. The Temsah Gas Field resides in the eastern sub-basin.

Petroleum Exploration

The first exploration campaign in the Temsah Gas Field was conducted by the Mobil Exploration Egypt Inc. in the late 1970s and early 1980s. From 1975 to 1981, Mobil drilled the Ras El Barr-1, Damietta-1, Temsah-1 and Temsah-2, and Gebel El Bahr-1 and 1A, only one, Temsah-2, tested consistent hydrocarbons. Majority of these wells had to be abandoned prematurely due to drilling problems. In 1991, The International Egyptian Oil Company (IEOC) was awarded a license to begin exploring the area and made its first discovery in 1995 with the Denise-1 well. The IEOC has been operating the Temsah Concession since 1992 and activity in the concession was very intense in the beginning. In the first four years, ten wells were drilled in the region with eight of them being located over the Temsah Gas Field. In 1992, exploration began with 3D seismic surveys over the field that covered an area of 350 km² and from 1992 to 1995, 2000 km of 2D seismic lines were done over the rest of the concession. In 1995 and 1996 a large 3D survey was done on the northern and central part of the Temsah concession that covered an area of around 1200 km². January 1996 was the ending of the first exploratory period in the region which lasted four years. In 1998, Amoco and ENI signed a long term natural gas agreement for the Temsah gas field. The first natural gas began to be produced from the Temsah Gas Field in 2000. Temsah-3 well that was the first well drilled in 1993 by the IEOC turned out to be the most successful well in the history of gas exploration in the Nile Delta Basin. Temsah-3 well was tested to have more than 80 meters of net pay (gas and condensates). Gas reserves in the area have been estimated to have up to 3.9 tcf (trillions of cubic feet) of natural gas.

Tectonic History

The tectonic history of the Nile Delta Basin began during the Triassic-Jurassic period with NE-SW Pelusium shear development that is associated with the opening of the Tethys Ocean. Then the Tethys Ocean closed during the Late Cretaceous-Early Tertiary due to ENE Syrian Arc movement. The onlap of source rock with Late Cretaceous and Early Tertiary deep water sediments indicate fault movement that occurred in the Late Cretaceous. Then the rifting of the Red Sea and the Gulf of Suez caused NNW-SSE faulting during the Lower to Middle Eocene. The Tertiary saw a handful of tectonic activity beginning with N-S Baltim rifting that occured in the middle of the Nile Delta. In the western offshore region of the Nile Delta, the NW-SE trending Rosetta Fault developed and in the eastern offshore region of the Nile Delta, NW-SE Temsah fault developed. The Rosetta trend was created by transpressional movement along the Qattara Eratosthenes trend. The Temsah structure has a NW-SE anticlinal structure that lies along the Bardawil alignment which is made up of Miocene and pre-Miocene formations. The flower-like shape of this structure indicates a history of strike-slip movements.

Progression of the closing of the Neotethys Ocean

Lithostratigraphy

The formations of the Nile Delta Basin and the Temsah Gas Field include; The Qantara, Sidi Salem, Wakar, and Rosetta Formations.

Qantara Formation (Burdigalian)

The Qantara Formation is compromised of shales and carbonates that has intercalations of marl and sandstone and covers a major area of the Nile Delta. It is a source rock for the overlying Sidi Salem and Wakar reservoirs.

Sidi Salem Formation (Serravallian)

The Sidi Salem Formation has open to shallow marine shales with occasional interbeds of dolomitic marls, sandstone lobes and siltstones. In the Temsah concession, where it comes into contact with the Wakar Formation and occasionally the Rosetta Formation has a sharp upper boundary.

Wakar Formation (Tortonian)

The Wakar Formation is compromised of a complex system of turbiditic sediments is overlain by the Rosetta Formation and underlain by the Sidi Salem. The topography of the formation is characterized by a irregular paleo-relieft pattern that dips north and northwest. In northwestern section of the Temsah concession, it is completely eroded away and here the Rosetta Formation lays directly on top of the Sidi Salem.

Rosetta Formation (Messinian)

The Rosetta Formation consists of an anhydrite sequence that is interbedded with thin claystone beds. The Rosetta Formation was deposited during the Messinian Salinity Crisis.

Source Rocks

The Qantara and Tineh formations are considered potential source rocks for the overlying the Sidi Salem and Wakar formations. The Tineh Formation is made of woody kerogen that has a terrestrial origin and has good to fair potential for gas and condensate and has a low to medium hydrogen index (HI) with values vary from 100 to 300. The Qantara Formation is characterized by good to fair potentiality for gas (HI = 46–183).

Above these sequences, the shale sequences of the Sidi Salem Formation are characterized by poor to fair source rock potential for gas (HI = 50–130). The shale are considered thermally mature source rocks for hydrocarbon generation. The shale sequences of the Wakar Formation showed a low HI (≤ 65).

Reservoir Rocks

The main reservoir targets in the Mediterranean Basin are in the Middle to Upper Miocene and Pliocene sections where the variety of depositional systems (fluvial, shallow marine and deep water turbidites) in the Nile Delta increased the potentiality for reservoir rocks. Their depositional systems offered attractive opportunities for gas and condensate exploration in the offshore deepwater areas.

The Sidi Salem Formation has sand lobes that have good petrophysical properties that act as stratigraphic traps within the main shale sequences of the formation. These sand lobes are the main gas reservoirs in the Temsah field, having 23%–30% as effective porosity and a permeability range of 63–297.4 md. Isoparametric maps of the Sidi Salem Formation show that the sandstone lobes can be considered good reservoir rocks, with the best characteristics being recorded in the crest of the structure to the north and west central parts of the Temsah field, through Temsah-3, Temsah-8, Temsah-2 and Temsah-1 wells.

The calcareous to dolomitic sandstone of the Wakar Formation reaches its optimal reservoir characteristics in the wells that penetrate its anticlinal crest structure and southern flank to the north of the Temsah field (Temsah-3 and Temsah-8 wells). The permeability of Sidi Salem reservoir rocks is mostly controlled by the porosity, whereas in the Wakar Formation the reservoir rocks are governed by porosity and water saturation. The Wakar Formation is considered a secondary stratigraphic reservoir target in the Temsah field since it does not extend through the entire field; and is partially absent in the central and northwestern parts.

The shaly sequences of the Kafr El-Sheikh Formation is not a drilling target in the Temsah gas field; however, sandstone fingers are occasionally seen throughout the formation and can be considered a good reservoir in Temsah-4 and Temsah-7 wells.

Seal Rocks

The Wakar and Sidi Salem reservoirs are potential seal rocks due to the stratigraphic trap nature where sand reservoir loves and lenses are enclosed by thick shale sequences. The Rosetta Formation also acts as an additional seal rock. The Pliocene rock sequences contain thick shale beds that serve as cap rocks for the Miocene and Pliocene reservoir sequences.

2004 Fire

In 2004, a fire broke out at the GSF Adriatic IV jack up drilling rig that eventually spread to a natural gas production platform in the Temsah field. The drilling rig eventually sank and was not salvageable while the platform was damaged beyond repair and was ordered by Egypt to be destroyed. The fire was caused by the overflow of natural gas during drilling that was brought under control but eventually was reignited. All 150 workers on the platform and 79 workers on the drilling rig were evacuated safely with no injuries or casulties. The damage was estimated to be around $190 million (current value is estimated to be around $279 million).