Produced water is an inextricable part of the hydrocarbon recovery processes, yet it is by far the largest volume waste stream associated with hydrocarbon recovery. In a C-field in South Oman, the produced water has been disposed in the aquifer zone of the producing formation. The feasibility of alternative ways to dispose water at surface using alternative options is being evaluated with the objective of reducing (or completely stopping) this water disposal which has shown benefits in maximizing the recovery by reversing the pressure decline. A simple model has been used to quantify the benefits of produced water re-injection into the deep aquifer zone. Deep water disposal (DWD) has been on-going for over 20 years in the aquifer zone in the B-formation in this field in South Oman. All the produced water from the surrounding fields is sent for disposal near the field via the C-Field Processing Station DWD system. This DWD activity has provided important energy to the system as evident in the reversing reservoir pressure trend in field. However, due to various reasons, efforts are being put forward with the aim of replacing DWD with alternative ways of disposing produced water at surface. An integrated model has been built and calibrated to the field response and used to predict the field performance. The calibrated model recommends to continue pressure to the field through water disposal or injection system. The study predicts the complete discontinuation of DWD will put significant reserves at risk eroding the field value and has quantified the amount of water available for the alternative options for surface disposal. The study has also identified an opportunity to further optimize the solution for pressure maintenance and thereby, potentially improving the recovery from the field.
The South Oman clusters A and B have reclassified their Deep-Water Disposal wells (DWD) into water injection (WI) wells. This is a novel concept where the excess treated water will be used in the plantation of additional reed beds (Cluster A) and the farming of palm trees (Cluster B), as well as act as pressure support for nearby fields. This will help solve multiple issues at different levels namely helping the business achieve its objective of sustained oil production, helping local communities with employment and helping the organization care for the environment by reducing carbon footprints. This reclassification covers a huge water volume in Field-A and Field-B where 60,000 m3/day and 40,000 m3/day will be injected respectively in the aquifer. The remaining total excess volume of approx. 200,000m3/d will be used for reed beds and Million Date Palm trees Project. The approach followed for the reclassification and routing of water will: Safeguard the field value (oil reserves) by optimum water injectionMaintain the cap-rock integrity by reduced water injection into the aquifer.Reduce GHG intensity by ±50% as a result of (i) reduced power consumption to run the DWD pumps and (ii) the plantation of trees (reed beds and palm trees).Generate ICV (in-country value) opportunities in the area of operations for the local community to use the excess water at surface for various projects.Figure 1DWD Reclassification benefits Multiple teams (subsurface. Surface, operations), interfaces and systems have been associated to reflect the re-classification project. This was done through collaboration of different teams and sections (i.e. EC, EDM, SAP, Nibras, OFM, etc). Water injection targets and several KPIs have been incorporated in various dashboards for monitoring and compliance purposes. Figure 2Teams Integration and interfaces It offers not only a significant boost to the sustainability of the business, but also pursues PDO's Water Management Strategy to reduce Disposal to Zero by no later than the year 2030 This paper will discuss how the project was managed, explain the evaluation done to understand the extent of the pressure support in nearby fields from DWD and the required disposal rate to maintain the desired pressures. Hence, reclassifying that part of deep-water disposal volume to water injection (WI) which requires a totally different water flood management system to be built around it.
This paper describes the utilization of produced and treated formation water for planting trees and growing algae in large ponds; in a massive scale in South Oman. A detailed study has been carried out to assess the injection requirements for pressure maintenance in the producing reservoir and using the remaining excess pot-treated water for farming of the palm trees. The produced water has been used as disposal in formations deeper than the producing horizons in the past. The produced water was separated in a processing station that received gross production from a number of fields in South Oman. This water was disposed in the aquifer underlying a producing reservoir that has experienced pressure maintenance due to this disposal. The impact of this excess water disposal on the aquifer was studied to evaluate the risk of breaching cap rock integrity. The risk was not significant but to ensure "no damage to the environment and people" it was decided to reduce or optimize injection rates to maintain the reservoir pressure safeguarding reserves. In addition, the disposal of the water required significant amount of power equivalent to emitting significant amount of CO2 annually just for water disposal. The study was carried out using simple material balance methods to predict the pressure behaviour given an injection profile. The recommendations from the study have already been implemented to convert the deep-water disposal to injection in the aquifer. This has been achieved by the integration of number of interfaces from sub-surface to field operations. All the pieces are in place to take it the next level of execution that is to treat the water at surface for oil removal, hence rendering the water at acceptable quality levels for tree plantation and algae ponds. The project also aims in a future second phase to further treat the water to higher specifications allowing the use of it for agricultural purposes. This would introduce a commercial farm that will depend on this source of water. This would be a novel concept in South Oman where the treated water will be used for farming solving multiple issues at multiple levels namely helping the business achieve its objective of sustained oil production, helping local communities with employment via farming and helping the organization care for the environment by reducing carbon footprints.
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