As oil and gas fields mature, their natural strength that drives the oil or gas out of the subsurface formations declines until wells require help getting the oil out of the ground through artificial lift methods. For artificial lift to stay economically feasible, it is critical that the hydrocarbon production stays high and the cost to push them out stays low. If that is not the case, it makes more sense to leave the hydrocarbons in the reservoir. One of the many techniques used to increase oil production whilst keeping artificial lift cost low, is to optimally inject the well with chemicals.
There are approximately 15 techniques for artificial lift that are used by E&P (Exploration & Production) companies. The most common types include the use of mechanical pumping, ESPs (Electrical Submersible Pumps), and injecting lighter gas, chemicals or liquids to lift the hydrocarbons either continuously or in batches.
Chemicals that are injected in wells cause the fluid to become lighter, allowing the natural forces in the subsurface to push them out to the surface. Chemicals are also used to eliminate water from the reservoir. When wells mature, the amounts of hydrocarbons decrease in production, and the amount of water tends to increase.
Water blocks the pores, resulting in low reservoir permeability and thus induces a well back-pressure. This causes production to slow down or stop. By treating the water with chemicals, this back-pressure drops, allowing hydrocarbons to flow again. Chemical injection helps in other ways as well. It can help neutralize dangerous H2S accumulations, and remove aspartame fouling while reducing wax and residue build-ups. Thus, chemical injection can result in safe and long-term production from mature wells on artificial lift.
For artificial lift to be effective, it is critical that chemical injection be within an operative budget. The operator must know how much chemical to inject. Pumping less chemical will not eliminate the problems and pumping too much could result in waste. Chemical management systems (CMS) have sensors which continuously monitor well conditions. The injection rates are adjusted to match the exact need. Optimizing chemical injection incurs other advantages such as the reduction of pump repairs and a decrease in the risk of operator exposure to hazardous chemicals.
In artificial lift, the amount of chemicals required for injection varies during its two phases. More chemicals are needed while the well closes and builds up internal pressure and less when the well opens and hydrocarbons flow to the surface.It has the ability to adjust the injection rates as required while maintaining continuous chemical injection artificial lift. The figure below shows how this is achieved through the use of an advanced artificial list optimization feature.
The right chemical injection strategy can be a defining factor in an economically feasible artificial lift operation for wells. Chemical management systems can be the answer to help optimize artificial lift operations.
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