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Subject Visit the SIDI EL-ITAYEM OIL field Prepared by Salah SABERSCHOUL YEAR: 2011-201


An onshore field near Sfax, Sidi El Itayem was discovered in 1971 by Total's Company Franco-Tunisian of Petrols (CFTP). A small structure in a Triassic reservoir 7,500-7,800 feet deep, The field came on stream in 1972. The block called, Sfax-Kerkennah, is partly onshore and partly offshore first won by Total in 1968. In 1986, Total drilled additional wells in the northern part of the field's reservoir, where there was need for a greater density of holes. Output at Sidi El Itayem peaked at 8,000 b/d of 44 deg. API oil in 1977 but fell to less than 2,500 b/d in 1984. A gaslift system installed in the late 1980s enabled production to average between 2,500-3,000 b/d. But it has since declined steadily. In 1999 it produced 82,000 tons, down from 123,000 tons in 1996. ETAP expects the output to drop to 75,000 tons in 2000 and 69,000 tons in 2001. The nearby Sidi Behara field, developed as a similar Total-ETAP venture, ceased production in 1979. TotalFinaElf has remained the operator of both Sidi El Itayem and the Mahares field. Development of Mahares was completed in 1992 and the field began producing oil under a 30-year JV with ETAP. But this field now is only producing about 55 b/d, compared to 75 b/d in the first half of 1998. TotalFinaElf has a 37.5% stake in the 5,620 sq km offshore Marin Centre Oriental block, where Coparex is the operator (see above). The other 25% is held by Agip. TotalFinaElf has a 30% stake in the Isis offshore field, also operated by Coparex.

GEOLOGY OF THE DEPOSIT OF SIDI ELITAYEMThe main objective was : The Ypresian holding tank located at 2400 m. The Bartonien holding tank located at 1950 m.

SAFTY ADVICESAfter beginning the visit it is very important to take prevention acts like: Wearing a hard hat

Wearing a safety glasses

Wearing a safety shoes

2- GENERAL OVERVIEW OF SIDI EL-ITAYEM FIELD CFPThe first step ----visiting the extraction point1. Introduction:The extraction of petroleum is the process by which usable petroleum is extracted and removed from the earth. Target: give an overview of petroleum production


Locating the oil field and drilling:

After locating the oil field by the geologists and using the seismic surveys to search for geological structures that may form oil reservoirs; the oil well will be created by drilling a hole into the earth with an oil rig . . A steel pipe (casing) is placed in the hole, to provide structural integrity to the newly drilled wellbore. Holes are then made in the base of the well to enable oil to pass into the bore. Finally a collection of valves called a "Christmas Tree" is fitted to the top.2.

The Christmas tree valves:

Generally after drilling the well we use a special collection valves called Christmas Tree; there is some functions for it: Controlling the flow, usually oil or gas, out of the well. (A tree may also be used to control the injection of gas or water into a non-producing well in order to enhance production rates of oil from other wells.)

Regulating pressures

1. Oil extraction and recoveryPlatform data: In our production centre we located : 47 wells An oil under saturated for recovering presence of water in large amount :98 % of water with high salinity S= 120 g/l the total recovering during 43 years equal 17 % of deposit

Natural lift description (Primary recovery) :During the primary recovery stage, reservoir drive comes from a number of natural mechanisms..

Recovery factor during the primary recovery stage is typically 515%. The primary recovery per well = 120 m3/h While the underground pressure in the oil reservoir is sufficient to force the oil to the surface, all that is necessary is to place a complex arrangement of valves (the Christmas tree) on the well head to connect the well to a pipeline network for storage and processing. NOTE: in our visit we didnt see this stage but ; only the Christmas tree was fixed on the well head

Artificial lift systems description :Over the lifetime of the well the pressure will fall, and at some point there will be insufficient underground pressure to force the oil to the surface. After natural reservoir drive diminishes, secondary recovery methods are applied. The scondary recovery per well = 3 m3/h after GAS LIFT INJECTION The tertary recovery per well = 1 m3/h after

recovery techniques

They rely on the supply of external energy into the reservoir in the form of injecting fluids to increase reservoir pressure, hence replacing or increasing the natural reservoir drive with an artificial drive.1. The electrical submersible pumps (ESP)

The electrical submersible pumps , are used to bring the oil to the surface.Submersible pumps are used in oil production to provide a relatively

efficient form of "artificial lift", able to operate across a broad range of flow rates and depths. By decreasing the pressure at the bottom of the well, significantly more oil can be produced from the well when compared with natural production. The pumps are typically electrically powered and referred to as Electrical Submersible Pumps.

ESP systems consist of : Sub-surface components (found in the well hole) include: the pump motor seal and cables Surface components (housed in the production facility) include: the motor controller (often a variable speed controller), surface cables Transformers

The Variable Speed Drive (VSD)

The energy to turn the pump comes from a high-voltage (3 to 5 kV) alternating-current source to drive a special motor that can work at high temperatures of up to 300 F (149 C) and high pressures of up to 5,000 psi (34 MPa), from deep wells of up to 12,000 feet (3.7 km) deep with high energy requirements of up to about 1000 horsepower (750 kW)

1. Gas lift injection :

Gas lift is one of a number of processes used to artificially lift oil from wells where there is insufficient reservoir pressure to produce the well. The process involves injecting gas through the tubing-casing annulus. Injected gas aerates the fluid to reduce its density; the formation pressure is then able to lift the oil column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas-lift equipment.

2. Pump-jack : Also in artificial lift, the oil can be pumped up the tubing to the surface with a common artificial technique called beam pumper or the pump-jack (which the case in the sidi-litaym platform) It is used to mechanically lift liquid out of the well if there is not enough bottom hole pressure for the liquid to flow all the way to the surface. The arrangement is commonly used for onshore wells producing little oil. Pump-jacks are common in oil-rich areas.

The second step ----- Pipeline transport

The produced fluids flow though a plastic or steel flow line from the wellhead to a long, metal tank, called a separator Pipeline transport is the transportation of goods through a pipe. Oil pipelines are made from steel or plastic tubes with inner diameter typically from (100 to 1,200 mm). Most pipelines are buried at a typical depth of about (0.91 to 1.8 m).

The oil is kept in motion by pump stations along the pipeline, and usually flows at speed of about 1 to 6 meters per second (3.3 to 20 ft/s)

The third step ----- stage separationDefinition It is an operation in which the well stream is passed through two or more separators that are arranged in series. The crude oil will be separated by gravity from the oilfield brine (the salt water) and gas in the separator The first separator is called first-stage separator the second separator is called second-stage separator Additional separators are named according to their position in the series The objective of stage separation

To maximize the hydrocarbon liquid recovery To provide maximum stabilization to the resultant phases (liquid and gas) leaving the final separator Separators types horizontal separator : A vessel, with its cylindrical axes parallel to the ground that is used to separate oil , gas and water from the produced stream. Vertical separator : A vessel with its cylindrical axes perpendicular to the ground that is used to separate oil, gas and water from the production stream

After the stage separation the well stream will set in the

settling pond ; and we send the non useful gas to torch

The fourth step ----- storageStorage:

After separating the well stream; the crude oil then flows through a flow line to large metal tanks, stock tanks, where it is stored.

Transportation:When the stock tanks are filled with oil. A service company picks up the oil with a tank truck and takes it to the refinery (skhira) (Or) The oil is transferred to a pipeline and taken to the refinery (skhira)