World First Polymer Injectivity Test in High Salinity and High Temperature Carbonate Reservoir, Case Study from a Giant Reservoir in UAE

Abstract

Polymer flooding is a mature EOR technique successfully applied commercially in sandstone reservoirs and at the pilot stage in carbonate reservoirs. However, all previous pilots in carbonates reservoirs were implemented in relatively low temperature and low salinity conditions. No field application of polymer in carbonate was implemented in the last 25 years. In recent EOR screening studies for carbonate reservoirs in Abu Dhabi, polymer based EOR techniques were identified to target by-passed oil in heterogeneous/layered reservoirs The main challenges for polymer based EOR processes in ADNOC reservoirs is to find a stable polymer under the extreme conditions of high temperature/high salinity/high content of divalent cations which can be injected in carbonate reservoirs. An extensive laboratory program initiated 10 years ago led to the development of a polymer rich in Sodium Acrylamido tertiobutyl Sulfonate (ATBS). Thermal stability, bulk and in-situ rheology, adsorption and injectivity performed and the polymer was found suitable for the harsh conditions of ADNOC reservoirs. A de-risking strategy was designed in which a polymer injectivity test (PIT) followed by a multi well pilot are performed before the full field implementation of polymer based EOR for a number of ADNOC reservoirs. This paper describes in details the main steps of the successful PIT recently carried out including: the selection of the candidate well and the injection skid, the test design, its execution, the polymer solution quality management and the operational challenges faced during the pilot. The polymer Injectivity Test was conducted for 4 months and concluded by February 2020. A total of 150,000 barrels of viscous solution was successfully injected into the reservoir. This paper also details the real time surveillance and injection monitoring plans implemented during the test period for real time assessment of the skid delivery and the well response. This Injectivity test achieved the designed Key Performance Indicators related to polymer solution quality, viscosity, concentration, injection rate and skid running time. The dedicated surveillance and injection monitoring plan designed and implemented during this pilot, enables to confirm the good performance of the polymer during PIT period. Furthermore, PIT results showed good performance of Polymer in terms of viscosity, Injectivity at target rate and concentration. This paper also addresses the impact of water quality on polymer viscosity and skid operation. This paper presents field results for a new polymer developed for carbonate reservoirs at HT/HS. This successful Polymer Injectivity test qualified the new polymer for field application at harsh carbonate reservoir conditions. Results from this world first Injectivity test opens a new area of possibilities to improve recovery in giant heterogeneous carbonate reservoirs in ADNOC and in the Middle East.

Analysis and Simulation of Polymer Injectivity Test in a High Temperature High Salinity Carbonate Reservoir

“…The single-well polymer injectivity test was performed as part of a larger project to implement full-field polymer flooding in a giant carbonate reservoir in the Middle East that is characterized by harsh temperature and salinity conditions up to 120 °C and 250,000 ppm, respectively [ 19 , 20 ]. The objective of the test was to evaluate polymer injectivity at target rates and concentrations in order to obtain information that would help optimizing the design of later stages in the project.…”

“…According to Rachapudi et al, 2020 [ 19 ], a single water injection well was completed in the targeted high permeability zone with a perforation interval of 20 m. Water injection baseline of 13 months was then established prior to polymer injection with rates ranging between 80 and 1,300 m 3 /day. During water injection, multi-rate production logging tool (PLT) logs were conducted to assess vertical injection distribution.…”

“…The test was the first of its kind to be performed ever in a HTHS carbonate formation. For more details about the injection scheme and the field trial, see Rachapudi et al, 2020 [ 19 ] and Hinestrosa and Masalmeh, 2021 [ 20 ].…”

Updated Perceptions on Polymer-Based Enhanced Oil Recovery toward High-Temperature High-Salinity Tolerance for Successful Field Applications in Carbonate Reservoirs

“…In recent decade, several novel synthetic polymers, such as modified HPAM-based polymers have been extensively studied for cEOR field pilot projects globally and in varying reservoir conditions [ 44 , 78 , 104 , 169 , 176 , 202 , 203 , 204 , 205 , 206 , 207 , 207 ]. Nevertheless, to the best of our knowledge, there have only been a few polymer flooding projects undertaken in carbonate reservoirs [ 175 , 208 , 209 ].…”

“…Employing a de-risking strategy involved polymer injectivity test ( ) followed by a multi-well pilot that was conducted before the final field implementation of polymer-based cEOR reservoir for several ADNOC reservoirs. The PIT took four months to be completed in February 2019 which was at a 250 temperature and salinity ppm conditions, with low H S content [ 206 , 213 ]. A total of barrels of viscous solution was expended for injection into the reservoir.…”