For emerging oil exploration and production (E&P) operators in Uganda, water management is not only going to be about managing direct line-item costs but about mitigating risk. E&P operators in Uganda must assess the operational risk and impacts on capital expenditures (CapEx) and operating expenses (OpEx) as well as manage challenges from increased regulatory oversight of the National Environmental Management Authority (NEMA), and public scrutiny. These operating companies must effectively prioritise water management in oil production, better mitigate environmental risk, and improve operational excellence, while protecting millions of investment fund in potential earnings.
Water is especially vital in oil E&P operations. Once reliant on conventional vertical drilling and completion techniques, E&P companies have moved to unconventional drilling and completion processes—specifically, horizontal drilling and hydraulic fracturing—to access previously inaccessible resources. Water is a significant part of the unconventional production processes, and managing its use and disposal throughout the value chain is complex. Specific water-management strategies vary by individual well, depending on where it is in the production cycle.
Water injection is one of the most useful techniques for enhancing the production of oil from petroleum reservoirs. This is not only because of the low cost of water but also because of the characteristics of the water which help sweep the trapped oil efficiently. In order for the process to be successful, the water must be treated prior to being injected. Any toxicity, oxygen or silt within the water could not only damage the machinery being used in the injection process but also risk damaging the oil it will come into contact with. It is therefore vitally important that a number of processes are undergone by the water before it is put to use. Therefore, all of the water used goes through an extensive filtration and processing process.
In certain cases, if the water was not injected, the developed reservoir may only produce as little as 3.4% out of the original oil in the reservoir as a result of sharp decrease in the reservoir pressure which is not enough to support the oil production. On the other hand, the application of water injection to sustain and support the average reservoir pressure could lead to increasing the production of oil to reach more than 31% out of the original oil in the reservoir. Thus, the application of water injection is a helpful technique for enhancing the production of oil.
Majority of wells to be drilled and completed onshore in Uganda could use horizontal drilling and water-based hydraulic fracturing programmes, which are far more water-intensive and pose very different management challenges than conventional E&P. The hydraulic fracturing process calls for large volumes of water for use in a fluid that is injected under pressure to create fractures that enable the flow of oil and gas. The fluid also contains small sand or ceramic particles, called proppant, that lodge within the fractures to keep the fracture sites open once the hydraulic pressure is released and the fluid flows out of the well bore. Today, hydraulic fracturing is a common practice both in conventional E&P, where it is used to extend the useful life of old wells, and in unconventional E&P. A typical hydraulic fracturing programme involving a conventional well requires approximately 25,000 barrels of water. An unconventional well can require up to 250,000 barrels of fluid during the completion process and generate large volumes of wastewater.
Yet one solution E&P operators in Uganda is looking at for their exploration and production activities is expanding reinjection at onshore and offshore sites. This is in recognition of the fact that water has a wide range of uses, including agriculture, food and hygiene. The aim is to minimize the water drawn from the environment, by deploying a type of circular process to avoid competing with or disrespecting other uses. So limiting water use and discharges into ecosystems is a choice for E&P operators, especially in the Albertine region of Uganda and the River Nile. This is the first option for responding to environmental concerns and balancing the demands of industrial efficiency and regulations. Produced water reinjection must adapt to each production site’s always different environmental, technical and regulatory requirements.
Total’s Pierre Pedenaud in an interview had this to say about water use in E&P operations in Uganda: “For example, in Uganda, at a future onshore site that will produce saline water, reinjection is mandatory because discharging it into freshwater meant for communities is out of the question.” (https://www.cnbc.com)
Professor of Environment and Sustainability