Production

Production is the phase of operation that deals with bringing well fluids to the surface and preparing them for the trip to the refinery.

Production operations include the following:

    Well Completion Artificial Lift Well Stimulation Fluid Treatment

Well Completion

Once the hole is drilled to the final depth, the completion of the hole begins.

Well completion is a function of:

    Formation Type Formation Pressure Production Scheme Number of Producing Zones

Open Hole Completion

There is no casing against the producing zone.

Used for:

   Hard limestone formations One producing zone Low pressure formation

Cased Hole Completion

Perforated Completion

   Perforating is the process of piercing the casing wall and the cement behind it to provide an opening through which formation fluids enter the well Most popular method of completing a well A perforating gun that carries several bullets (shaped charges) makes these opening

Cased Hole Completion

Wire-Wrapped Screen Completion

 Used to prevent sand production (from unconsolidated formations)    Sand can clog the well and may stop production Sand also damages equipment in the hole Slotted Liners with gravel packs are used to prevent sand production

Cased Hole Completion

Tubing

    After cementing the production casing, the tubing is installed in the hole Tubing is not cemented Tubing has a smaller diameter than the casing Tubing enhances production

Cased Hole Completion

Packers

   A packer is a ring made of metal and rubber that fits around the tubing It is used to seal off the space between the tubing and the casing, thus forcing the formation fluid into the tubing It separates the fluid pressure and fluid above and below the packer

Cased Hole Completion

Tubingless Completion

  Is used when the casing size is so small that there is no need for tubing Is used in small gas reservoirs that produce few if any liquids and have low fluid pressure

Cased Hole Completion

Multiple Completions

  Used to produce from two or more zones containing oil and gas A separate tubing string with packers is run in for each producing zone

Wellhead

A wellhead is installed on the well to:

  Control the paths and flow rates of reservoir fluids Seal the well

Wellhead components

   Casing Head Tubing Head Christmas Tree

Natural Drive Mechanism

Oil is produced from the reservoir by the natural energy stored in the reservoir.

Such production is called Primary Recovery.

Natural energy in the reservoir may result from the following:

    Oil and Gas Expansion Hydrostatic Pressure Hydrodynamic Pressure Gravity

Natural Drive Mechanism

Thus, depending on the natural energy source, the following natural drive mechanisms are:

    Gas Drive  Solution Gas Drive  Gas-Cap Drive Water Drive Gravity Drainage Combination Drive

Natural Drive Mechanism

Solution Gas Drive

 Main driving force is the dissolved gas expansion     Due to gas expansion, the reservoir pressure depletes very fast Oil may not have enough pressure to reach the surface The recovery of oil is small A supplemental energy is required to produce more oil

Natural Drive Mechanism

Gas-Cap Drive

   Similar to solution gas drive except the free gas is expanding and further driving the oil out of the reservoir Higher recovery than Solution gas drive A supplemental energy is required to produce more oil

Natural Drive Mechanism

Water Drive

   Free water (under high pressure) that is beneath the oil drives the oil up the well Active Water Drive  Water fills all the empty pores that produced oil once occupied Partial Water Drive  Water fills part of the empty pores

Natural Drive Mechanism

Water Drive

 The reservoir pressure remains almost constant; thus,   Oil is produced until water level reaches the perforation The oil recovery is much greater than gas drive mechanism

Natural Drive Mechanism

Combination Drive

  Gas Drives, Water Drives and Gravity all act at the same time to drive the oil out of the reservoir, into the well and to the surface.

This type of drive has the highest oil recovery because of the energy available to drive the oil out of the reservoir.

Artificial Lift

The energy in the reservoir vanishes after producing for a period of time (for Gas Drive Reservoir).

Up to 95% of the oil remains in the reservoir because of the lack of energy and driving force.

Thus, an artificial source of energy should be added to the well to drive the oil to the surface.

Artificial Lift

Two methods to drive the oil from the bottom of the hole to the surface are:

  Lightening the fluid column in the well by reducing the fluid density in the well.

 Gas Lift Adding a mechanical energy (pump) to push the oil upward.

  Sucker-rod pump Electrical Submersible Pump

Artificial Lift

Gas Lift

    Gas is injected in the space between the tubing and the casing.

Gas enters the tubing through special valves on the tubing that open at high pressure.

Gas mixes with the oil and pushes it to the surface.

Once the fluid column is lightened, the reservoir pressure pushes more oil higher into the well.

Artificial Lift

Sucker-Rod Pump

   The most common pump used onshore Used for wells with a low flow rate Relatively cheaper than other pump types

Artificial Lift

Electrical Submersible Pumps

   Used for high flow rate wells Can use several pumps to increase the flow rate Expensive

Well Stimulation

Hydraulic Fracturing

  Fracturing fluid is pumped at high pressure into the well until it parts (fractures) the formation Then Proppant is pumped into the induced fracture to keep it open and to create highly permeable channels

Well Stimulation

Acidizing

   Acid is injected into low permeability formations to create channels of high permeability It is also used to remove formation damage near the wellbore Mostly used in Carbonate reservoirs

Improved Oil Recovery (IOR)

40% to 95% of oil remains in the reservoir after the primary recovery stage is completed.

Improved Oil Recovery is used to recover as much of the remaining oil as possible.

Many different techniques are applied in the Improved Oil Recovery stage.

Improved Oil Recovery (IOR)

Improved Oil Recovery (IOR)

Water Flooding

   Water is injected into the reservoir from the injection well Injected water pushes the oil to the producing well Injected water helps in:   Increasing oil recovery Pressure maintenance

Improved Oil Recovery (IOR)

Chemical Flooding (Surfactant flooding)

 A surfactant (Surface acting agent) is mixed with water and injected into the reservoir  Surfactant reduces the surface tension between the oil, water and the rock. Thus, freeing oil as droplets and pushing them to the producing well

Improved Oil Recovery (IOR)

Thermal Recovery (Steam Flooding)

 Steam is injected in the reservoir that contains heavy high viscosity immobile oil   Steam reduces the oil’s viscosity and makes it more moveable The reduced viscosity oil is then produced

Surface Handling of Well Fluids

Produced oil is usually accompanied by:

    Water Water Vapor Solids, such as:   Sand Shale Sediments Contaminants, such as:   Carbon Dioxide Hydrogen Sulfide

Removing Free Water

Free water is removed by using the Free Water Knockout (FWKO).

Free water is separated from oil by the force of gravity.

Separating Liquids from Gases

Gas can simply be separated from liquids by passing the fluid through a tank and letting gravity take its action.

Separators utilize centrifugal forces as well as gravity to separate well fluids.

Separating Liquids from Gases

Horizontal separators might be used to separate gas from liquids.

Multistage separations might be used to separate more gas from liquids.

 The second separator removes more gas from the liquid because the lower pressure allows more hydrocarbons to vaporize

Controlling Paraffin

Paraffin is a white hydrocarbon wax found in petroleum.

 It reduces the efficiency of the separators  It makes the separator inoperable

Steaming and Solvents are an effective way to prevent wax deposition. Coating the internal surface of the separators with a plastic to which the paraffin will not stick prevents paraffin build up.