Evaluation of Ultrahigh-Temperature-Resistant Preformed Particle Gels for Conformance Control in North Sea Reservoirs

Abstract

Summary Preformed particle gels (PPGs) are 3D, crosslinked, dried polymer particles that can swell to several hundred times on contact with formation water. PPGs have been used extensively to control water production problems in reservoirs with conformance problems. The current state-of-the-art PPGs are polyacrylamide-based hydrogel compositions which lack long-term thermal stability under high-temperature and -salinity conditions. There are many oil reservoirs across the globe exhibiting conditions of temperatures higher than 120°C with high salinity. A novel ultrahigh-temperature-resistant PPG composition (DMA-SSS PPG) was designed to fill up the technology gap between existing polyacrylamide-based PPG technology that degrades readily over 110°C temperatures. DMA-SSS PPG exhibited excellent thermal stability for greater than 18 months in North Sea formation and formation water environments at 130°C. DMA-SSS PPG described herein showed swelling capacities of up to 30 times in different salinity North Sea brines. DMA-SSS PPG’s physiochemical properties like swelling, swelling rate, and rheological behavior were studied as a function of temperature and salinity. DMA-SSS PPGs showed excellent elastic modulus (G’) of about 3200 Pa in formation water of 90% water content. Thermostability of DMA-SSS PPGs was assessed at 130 and 150°C in North Sea brines with different salinity conditions. DMA-SSS PPGs proved to be stable for more than 18 months without losing molecular integrity. Thermostability was further confirmed through different metrics such as cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CPMAS 13C NMR), thermogravimetric analysis (TGA), and morphology. Laboratory coreflood experiments were performed to demonstrate the plugging efficiency of open fractures and effectiveness in reducing the permeability. DMA-SSS PPG comprehensive evaluation confirms its novelty for excellent hydrothermal stability, thus can be used to control water production problems for mature reservoirs exhibiting conditions of high salinity and high temperature.

A Research Progress of CO-Responsive Plugging Channeling Gels

“…Acidic and high-temperature, high-salinity environments can accelerate particle degradation and dehydration [31]. The degradation products may contain ketone, aldehyde, carboxylic ester groups, and monomer units, which can adsorb onto mineral surfaces, causing harm to the reservoir [32] and they are poorly adapted to low-permeability reservoirs [16]. Although polymers with temperature, salt, and acid resistance have been developed, their high costs make them economically unfeasible for widespread use.…”

Progress of Research into Preformed Particle Gels for Profile Control and Water Shutoff Techniques

“…After 18 months of aging at 150 • C, as shown in Figure 4, no degradation or dehydration was observeda nd the color change was due to residual oxygen. NMR spectra and SEM images indicated that the original chemical composition and crosslinking network structure were maintained even after aging; Schuman et al [51] investigated the performance of HT-PPGs under North Sea reservoir conditions, where the formation water salinity was approximately 7.6 × 10 4 mg/L, and the reservoir temperature ranged from 130 to 150 • C. The swelling ratio of HT-PPGs could reach over 30, and its stability lasted for more than 18 months, demonstrating excellent thermal stability and chemical stability. In simulation core experiments, HT-PPGs were able to reduce the permeability of 2 mm fractures to a millidarcy level.…”

Development of Nanomontmorillonite-Reinforced Terpolymer Gels for High-Temperature Petroleum Reservoirs

“…1−3 However, the original natural energy supply of these high-temperature reservoirs is usually very limited, and the reservoir permeability exhibits strong heterogeneity characteristics, leading to frequent occurrences of small volumes affected by water shut-off and even rapid excessive water production in oil production wells. 4,5 Therefore, it is urgently needed to study chemical flooding systems for hightemperature reservoirs to plug high-permeability water pathways and thereby improve oil recovery. 6,7 Commonly used chemical plugging systems mainly include in situ cross-linked polymer gels, particle gels, and foam gels.…”

“…With the increasing demand for oil and gas resources and the continuous decrease recoverable conventional oil and gas reserves, more and more oil companies are turning their development goals to deeper, high-temperature petroleum reservoirs. − However, the original natural energy supply of these high-temperature reservoirs is usually very limited, and the reservoir permeability exhibits strong heterogeneity characteristics, leading to frequent occurrences of small volumes affected by water shut-off and even rapid excessive water production in oil production wells. , Therefore, it is urgently needed to study chemical flooding systems for high-temperature reservoirs to plug high-permeability water pathways and thereby improve oil recovery. , …”