Gas Injection

Horizontal Pumping Systems

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Category Description

Gas injection is the process of injecting natural gas (miscible and immiscible) or nitrogen (immiscible) to the reservoir, to push the oil to a producing well. The purpose of immiscible natural gas (dry gas) and nitrogen injection is to maintain pressure in the reservoir and create a gas cap. Sometimes nitrogen is used to capture oil that was trapped, as well.  Miscible natural gas (lean gas, LPG or rich gases), on the other hand, is used due to its ability to mix with oil, also known as miscible with oil.

Why it is required? Oil and water cannot be mixed into a homogeneous liquid, which in turn makes it less effective when water is used to push the oil. However, if the injected gas is miscible with oil, it will become a homogenous mixture, that will expand and allow the forces of injected lean gas to be used effectively, moving oil more easily towards the well. This method needs a high reservoir pressure in order to work effectively, as well as sources of economically cheap gas, normally lean gases (residual gas -methane and ethane).

It is important to make a distinction between gas injection and gas lift, as these are two different processes. In gas injection, as part of EOR, gas is injected through separate injector wells that are usually spread across the field in a predetermined manner. Gas lift, on the other hand, is an artificial lift method, whereby a pressurized gas, produced by a nearby well, is injected continuously or intermittently into the production tubing to lift the fluids. Injected gas travels to the reservoir through a gas lift valve at a certain depth. The underlying principle of the gas lift method is that gas reduces the density of the fluid by aerating it with gas bubbles. This, in turn, reduces bottom-hole pressure, aiding fluids from the reservoir to travel to the wellbore faster and easier.

While onshore logistics makes it easier to conduct a gas injection Enhanced Oil Recovery (EOR) project, in the offshore environment it is a lot more complex, challenging and costly, due to the fact that existing infrastructure was not designed to accommodate it, in terms of weight, space,  handling capacity and power. Depending on the size of the project, a specialized platform might be required to conduct offshore gas injection EOR projects. There are a number of constraints that should be considered and planned in advance, such as tanks and storage capacity, manning capacity to accommodate the required crew, pumping and supply capacity. In general, best practices and facilities for onshore gas injection EOR may not apply offshore. 

Feeding gas is a huge challenge that may be too costly to overcome, due to high H2S content in the natural gas available in the region. 

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Supply & Demand Dynamics

Global demand for Gas Injection EOR services will continue to be the second preferred method, after the thermal recovery option. However, with more emphasis on the environment and improved technology, the economics of CO2 EOR will result in higher utilization of this particular method and reduce the demand for gas injection EOR.

In the GCC, this change will be particularly evident due to power generation requirements. As a result of the growing population in the region and efforts to maintain and increase oil production, it is becoming more challenging to meet the demand for natural gas to cater to power generation, gas re-injection projects and steam generation. Hence, focus on other EOR methods, such as CO2, will be evident in the years to come and greatly affect any appetite for gas injection EOR projects.

Application of gas injection (miscible) projects in the GCC is limited to Harweel field in Oman and to a lesser extent in the Abu Al Bukhoosh field in UAE.

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Cost & Price Analysis

EOR production is considered as a project in itself and requires a large number of equipment and packages.  Studies, pilot projects, engineering design, equipment procurement, feedstock planning, drilling, and other materials, play an important role in EOR projects. Upfront capital costs in EOR projects are significant.


Availability of gas, its opportunity cost and infrastructure re-development play one of the key roles in cost basis for any gas injection EOR.

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Strategy

Almost every EOR project is bespoke and requires a large number of studies, pilot projects, and simulation.  As a result of this, equipment and packages are not standard and may require bespoke engineering and manufacturing every time, which in turn reduces the diversity of available suppliers, increases costs and lead times.

The most critical levers that would influence the costs and procurement decisions are 

  1. A comprehensive FEED study
  2. Analysis of the supplier market and their capabilities.

While there are numerous engineering companies providing the services of FEED studies, companies who specialize in the EOR studies and consultancies are in a better position to produce a more valuable and meaningful FEED - as they have large exposure to varus EOR projects. 

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