Injection – Injection wells are used to inject gas or water into the reservoir. The purpose of injection is to maintain overall and hydrostatic reservoir pressure and force the oil toward the production wells.

Artifical lift
Production wells are either free flowing or “lifted”. A free flowing oil well has enough downhole pressure to reach suitable wellhead production pressure and maintain an acceptable well flow. If the formation pressure is not sufficient, the well must be artificially lifted to maintain production.

Rod pumps – Sucker rod pumps, also called donkey pump or pump jack, are the most common artificial lift system used in onshore oil and gas extraction. A motor drives a reciprocating beam, connected to a rod passing into the tubing via a stuffing box. The sucker rod continues down to the oil level and is connected to a plunger with a valve.

On each upward stroke, the plunger lifts a volume of oil up and through the wellhead discharge. On the downward stroke it sinks, allowing oil to flow though the valve. The motor speed and torque is controlled for efficiency and minimal wear with a pump off controller

ESP (Electrical submerged pump) – The pumping mechanism is inserted into the well. The motor, the progressive cavity or a centrifugal pump hangs down the tubing.

Gas lift – Gas is injected into the well flow to reduce the specific gravity of the wellfluid such that the wellflow may be started or maintained even if the well pressure decreases below the pressure from vertical oil column.

Plunger lift – The plunger lift is normally used on low pressure gas wells with some condensate, oil or water, or high GOR wells. In this case, the well flow conditions can be such that liquid starts to collect downhole and eventually blocks gas so that the well production stops. In this case, a plunger with an open/close valve can be inserted in the tubing. A plunger catcher at the top opens the valve and can hold the plunger, while another mechanism downhole closes the valve. The pressure build up when the valve is closed pushes the plunger and liquid column up to the wellhead.

Ejectors – If the production system has available pressure (ie. high pressure wells, gas lift or gas injection) some of this energy may be used to boost low pressure wells by use of ejectors.

The available hig pressure, gas or liquid flow is routed through the ejctor that by a nozzle generates a underpressure or suction that is used to reduce the wellhead back pressure such that the low pressure wells may produce even if the well pressure is too low.

Well workover
Over time the productivity of many wells decreases due to residue buildup, sand erosion, corrosion or clogging. For maintainance and service well workover operations are performed.

Time saving, through tubing operations are executed through the pressure control devices at the well head, without “killing the well” by filling the casing with mud or other fluid to create a hydrostatic head.

Well workover or well intervention is carried out using various tevhniques and tools such as ; wireline, slick line, snubbing, coiled tubing and injection.

Fracture acidizing or matrix acidizing – Hydrochloric acid (HCL) is used to open up calcareous reservoirs and to treat accumulation of calcium carbonates in the reservoir structure around the well.

Hydraulic fracturing – A liquid is pumped down the well and into a formation under pressure such that the formation crack open, forming passages through which oil can flow into the well bore. Sand grains, aluminum pellets, walnut shells, glass beads, or similar materials (propping agents) are carried in suspension by this fluid into the fractures. When the pressure is released at the surface, the fractures partially close on the propping agents, leaving channels for oil to flow through to the well.

Hydraulic fracturing is an essential technology for unconventional shale gas and liquids extraction.

Explosive fracturing – Explosives are being used to fracture a formation.

Flushing – Flushing out drill fluids or other deposts in side the well bore.

Other
A variety of other techniques and tools are being used to enhance production this includes optimisation of the production or process plant hardware but also simulation, control and monitoring enhancements.