van den Hoek, Paul (Shell) | Mahani, Hassan (Shell Intl. E&P Co.) | Sorop, Tibi (Shell) | Brooks, David (AAR Energy) | Zwaan, Marcel (Shell Intl. E&P Co.) | Sen, Subrata (Shell India Markets Private Ltd) | Shuaili, Khalfan (PDO) | Saadi, Faisal (PDO)
This has a significant impact on pressure decline signature as exhibited during Pressure Fall-Off (PFO) tests. Therefore, applying a different PFO interpretation method, compared to conventional approaches for Newtonian fluids is required. This paper presents a simple and practical methodology to infer the in-situ polymer rheology from PFO tests performed during polymer injection. This is based on a combination of numerical flow simulations and analytical pressure transient calculations, resulting in generic type curves that are used to compute consistency index and flow behavior index, in addition to the usual reservoir parameters (kh, faulting, etc.) and parameters relating to (possible) induced fracturing during injection (fracture length and height). The tools and workflows are illustrated by a number of field examples of polymer PFO, which will also demonstrate how the polymer bank can be located from the data.
Mahani, Hassan (Shell Intl E&P Co) | Sorop, Tibi (Shell) | Ligthelm, Dick Jacob (Shell Intl E&P BV) | Brooks, David (Shell Intl E&P Co) | Vledder, Paul (Syria Shell & AFPC) | Mozahem, Fadwa (Al Furat Petroleum Co.) | Ali, Younes (Al Furat Petroleum Co.)
Low-salinity water injection is an emerging IOR/EOR technique, applicable to mixed-to-oil-wet sandstone reservoirs. This paper describes the field response for two large fields: Omar (secondary flood) and Sijan (tertiary flood). The data were analyzed using analytical and numerical modelling tools. This included evaluation of scaling numbers, mixing and dispersion and calibration. Insight was obtained on relevant drive mechanisms.
The responses to low-salinity flooding differ for the two fields:
• In Omar, a dual-step water-cut development was observed, which is characteristic for a change in wetting state. Our interpretation is that in this field, viscous forces provide the dominant drive mechanism, which is favorable to low-salinity flooding. We were able to history match the low-salinity response using a simple conceptual model.
• In Sijan, the low-salinity flood appears to be still immature and breakthrough of low-salinity water has not (yet) been observed. The reasons for the muted response thus far are explored, including a rather strong buoyancy effect caused by the higher permeability of the block, and the significant effect of injectant mixing with the highly saline aquifer.
A proposal is made for a workflow on how to apply this analysis to future low-salinity flooding implementation in field cases.
Al Azri, Nasser Said (Petroleum Development Oman) | Al Ajmi, Widad (Petroleum Development Oman) | Kazzaz, Ahmed (Petroleum Development Oman) | Ramalingam, Sankaranarayanan (Petroleum Development Oman) | Morshidi, Abulaziz (Petroleum Development Oman) | De Kruijf, Alexander (Petroleum Development Oman) | Jamal, Esam Abubaker (Petroleum Development Oman) | Al Busaidi, Iman Khamis (Petroleum Development Oman) | Al Mahrouqi, Abdullah (Petroleum Development Oman) | AlKharusi, Badar (Petroleum Development Oman) | Brooks, David (Shell Intl. E&P Co.)
Implementing Enhance Oil Recovery techniques in heavy oil reservoirs with strong bottom water drive has been a challenge in the oil industry. This paper describes an Enhanced Oil Recovery process in which polymer is injected into a clastic reservoir with a strong bottom aquifer drive bearing heavy-oil (250-500 cP). The high reservoir permeability (2-5 Darcy) enables stretching the viscosity limit of a standard polymer application.
The presence of a strong bottom aquifer maintains high reservoir pressure, which could provide a challenge to injectivity. The close proximity of injectors to the oil water contact reduces the efficiency of the polymer flood through water fingering, and polymer loss to the aquifer. To best understand details of the influence of aquifer on the recovery process, test different development scenarios and address key uncertainties, detailed simulation study was conducted. The simulation results showed that the optimum development concept which would help reduce impact of polymer loss to the aquifer would be to utilize the currently existing and future horizontal producers, augmented with additional infill horizontal injectors placed approximately mid-way in the oil column. Optimization of the development was performed using the simulation model where the polymer viscosity, slug size, and injector location were optimized for net present value.
Uncertainty analysis using the simulation model showed that factors such as poor injectivity, poor conformance control and high kv/kh ratio have negative impact on process efficiency. To address and mitigate these key risks and uncertainties a number of activities are underway. These activities include intensive laboratory tests, field injectivity test and a field trial where polymer is injected in newly drilled injectors. The paper discusses study to identify the optimum development concept, key uncertainties and associated risk reduction activities. Finally, this paper discusses the design and the surveillance aspects of the upcoming field trial.
Brooks, David (Shell Intl. E&P Co.) | De Zwart, Albert Hendrik (Shell Intl. E&P Co.) | Bychkov, Andrey (Shell) | Azri, Nasser (Shell International EP) | Hern, Carolinne (Shell) | Al Ajmi, Widad (Petroleum Development Oman) | Mukmin, Mukmin (Petroleum Development Oman)
The primary recovery of a medium-heavy oil reservoir with a strong bottom aquifer is generally poor. The introduction of horizontal wells that are drilled at the top of the oil column has improved the oil recovery. However, even horizontal wells suffer from fast water breakthrough that leads to oil production at a high water cut. Given the low primary recoveries, such fields are attractive EOR targets.
In situ combustion (ISC) is a displacement process generally applied to medium-heavy oil reservoirs in order to increase oil production by reducing the oil viscosity. In thick reservoirs (thicker than 10 meters), oil recovery could be severely challenged by gravity override of the injected gasses. In reservoirs without active aquifers, a significant part of the incremental oil is produced by gravity drainage after breakthrough.
We propose an ISC strategy where an infill producer is drilled close to the oil-water contact so that a significant amount of heat can be rapidly deployed in the middle and upper sections of the reservoir. Subsequently, the aquifer is used to sweep the warm oil through the heated zone towards the producers. The ISC process is compared with steam injection that also employs an additional infill producer. ISC and steam injection are used to deploy heat in the reservoir.
Numerical simulations show that the oil is produced at much lower water cut compared to the cold case (50-60 % versus 95%). Simulated oil recoveries increase significantly for both ISC and steam injection. A detailed comparison of these two processes is presented in this paper.