What is oil field water injection

If an oilfield relies on natural energy extraction, then the process of oilfield development is the process of oil reservoir energy consumption, that is, as the oilfield exploitation time increases, the pressure of the oil reservoir gradually decreases
.
If there is no considerable oil driving energy supplement, after the pressure of the oil reservoir drops below the saturation pressure, the natural gas dissolved in the crude oil will be a large amount of free out in the oil reservoir to enter the well first, so that the oil production of the well will continue to decline, the oil-gas ratio will rise, the properties of underground crude oil will deteriorate, the viscosity of crude oil will increase, the flow is difficult, and finally cause a large amount of "dead oil" remaining in the oil reservoir, which greatly affects the improvement
of the final oil recovery.
Therefore, in the process of oilfield development, it is necessary to maintain a reasonable reservoir pressure to maintain high yield and stable production of oilfields and wells, so as to achieve the purpose of
improving oilfield recovery and oilfield development efficiency.

At present, most of the oilfields at home and abroad are using the method of injecting water into the oil layer to replenish the energy of the oil layer, and the oilfields exploited by such methods are called water injection development oilfields
.
The development of oilfield water injection can generally achieve a recovery rate of 35% to 50%.

1.
Water source and water treatment

1.
Water source

The amount of water required for water injection in oilfields is very large, which is roughly 150% to 170% of the pore volume of the water injection oil layer
.
At present, in addition to sewage reinjection, there are two major categories of water sources used for water injection: one is freshwater sources, and the other is saltwater sources
.
freshwater sources fresh water from rivers, rivers, lakes, springs and groundwater layers below the ground; The source of salt water is mainly seawater
.
The choice of water sources should be tailored to local conditions and decided
after economic and technical demonstration.

2.
Water treatment

Oilfield injection water is generally not clogged oil layer, do not corrode water treatment equipment is better
.
The water quality requirements for the injected water are determined by the specific conditions of each oilfield, in order to meet the requirements of the injected water quality, appropriate treatment measures are generally taken for the water source to meet the requirements of the injected water quality of
the oilfield.

At present, the water quality treatment measures commonly used in China's oilfields are as follows: (1) precipitation: the sedimentation tank (or tank) is precipitated by the gravity of the solid particles suspended in the water to remove the suspended solids
.
(2) Filtration: commonly used pressure filter and valveless filter to filter very small suspended solids and a large number of bacteria
.
(3) Sterilization: Whether it is sewage or clean water, it is necessary to use fungicides to sterilize
.
(4) Deoxygenation: Commonly used chemical deoxidation and vacuum deoxygenation to slow down the oxidative corrosion
of oxygen.

Second, the water injection station

The role of the water injection station is to boost the water from the qualified water source after treatment to meet the requirements of water injection pressure and water injection volume, so that the water is injected into the oil reservoir of the water injection well
.

The process of the water injection station is mainly composed of water source qualified water pipes, water storage tanks, high-pressure injection pumps, and water pipelines, of which the high-pressure multi-stage centrifugal pump is the most important equipment
of the water injection station.

3.
Water distribution room and water injection well

The high-pressure water of the water injection station flows into the injection well
after regulation, control and metering through the water distribution room.
The water distribution room is the operation room that controls and regulates the injection amount of the injection well, which is generally divided into a single well water distribution room and a multi-well water distribution room, and the single well water distribution room is used to control and regulate the injection amount of the injection well; The multi-well water distribution room can generally control and adjust the water injection volume of multiple injection wells, which is more commonly used
.

A water injection well is a development well
designed for water injection according to the development plan.
The daily management of the water injection well is mainly to implement the production and injection plan, inject water according to the allocation, timely analyze the changes in the layered water absorption capacity, and find out the reasons so as to take effective measures
.
In order to inject water, slow down interlayer interference, and prevent the injecting water from being protruded by a single layer, the injection well usually uses a layered water injection process
.