Full Length ArticleA comprehensive investigation of polymer microspheres (PMs) migration in porous media: EOR implication
Introduction
The profitability of oil recovery stream is largely dependent on the oil production capability of the wells. However, massive water production during secondary and tertiary oil recovery is a challenging issue in a great number of oilfields worldwide. The past few decades had witnessed the extensive investigations and rapid development on water control in oil industry [1].
Peer scientists confirmed the functionality of gel particles in water control decades ago [2]. Recently, colloidal dispersion gels (CDGs) [3], [4], [5], preformed particle gels (PPGs) [6], [7], [8], [9], temperature-triggered micro-gels [10] and pH-sensitive micro-gels [11], [12], which were characterized by small particle size, high elasticity and outstanding dispersing capability, have drawn attention in both academia and industries. They were viewed as a game changer in in-depth conformance control and oil displacement [13], [14], [15], [16], [17], [18].
Nevertheless, the aforementioned gel particles are usually improperly used largely due to the difficulty in controlling their migration and plugging. Gel particles could obstruct the oil layers near injectors and caused the subsequent water to rapidly flow over entering the high-permeability layers again, which gave rise to poor conformance modification and water control [19], [20]. As a result, the migration of gel particles in porous media must be thoroughly understood [21], [22].
Zhang and Bai [23] investigated the factors affecting PPGs migration by transporting PPGs through open fractures. They observed that the injection pressure of PPGs increased with injection flow rates and reduced with the fracture width, the generated resistance factor declined as the flow rate was increased. Feng et al. [24] claimed that microgel could be transported into porous formation for conformance control more readily than polymer without any plugging barriers. Shi et al. [22] developed a microgel transport and retention model in reservoir rock, in which microgel can’t enter some water bypassed small pores. Instead, they are found to adsorb on the surface of large pores or be trapped at large pore throats. Coste et al. [25] examined the migration efficiency of PPG suspensions using core flooding experiments and confirmed that weak gels can penetrate to in-depth porous formation. Three types of PPGs motion in porous medium were defined, pass, breaking into pieces and pass, and plugging or jamming [7]. Yao et al. [26] conducted a series of shunt flow experiments using heterogeneous double-tube sand pack models. Their results showed that majority of PMs is inclined to migrate into the high-permeability layer, and thus reducing the shunt flow rate and permeability greatly. Gel particles captured by pore throats could re-migrate only when the driving pressure gradient exceeded the threshold pressure gradient, which largely depended on the pore-throat size, particle size, particle elasticity, particle quantity in bridges, and compaction degree of particles [15], [22]. Quite a number of the studies on the migration of gel particles used core samples or sand-pack as the porous medium in core flooding experiment. Although the pressure drop profiles and water cut data indeed reflected the migration behavior of gel particles in a macroscopic scale, they hardly helped the direct observation on the retention and plugging of particles in the porous medium. Therefore, the migration and retention of gel particles, crosslinked PMs, was then investigated through a series of visualization experiments, such as micro-visual model and capillary flow experiments, by Hua et al. [27], [28] and Lin et al. [29]. They claimed that crosslinked PMs were soft, flexible, deformable micro-gel particles that could adsorb, accumulate and bridge in the pore-throat channels to reduce water permeability. Unfortunately, the particle elasticity effect has not taken into consideration.
In this work, a new kind of gel particles named as PMs, were prepared through inverse emulsion polymerization. The physical properties of the prepared PMs were then characterized. The plugging mechanisms of PMs in porous medium were also proposed. The matching coefficients between the particle size of PMs and pore throat diameter of core were identified to quantify the matching relationship between PMs and pore throats, and thus allowing us to define the migration modes. Effects of the matching coefficients and particle elasticity on particle migration were also evaluated. In the end, the adsorption and desorption performance of PMs were briefly assessed. The primary objective of work was to elucidate the migration process of PMs in porous medium and provided insights for its future deployment in oil fields.
Section snippets
Materials
Acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N, N′-methylene double acrylamide (MBA), ammonium persulfate (APS), sodium bisulfite (NaHSO3), sodium hydroxide (NaOH), Span 80, Tween 80, acetone and ethanol ammonium persulfate (APS), sodium chloride (NaCl) were provided by Chengdu Kelong Chemical Co. and used as received. White oil was purchased from Chengdu Sidi Chemical Co., Ltd. The brine was supplied by Dagang Oilfield, China. The ionic composition was given in Table 1.
Morphology and particle size distribution
As shown in Fig. 1 and Fig. 3, the PMs were spherical micron-grade particles with milky white appearance. Fig. 2 showed that the initial particle size distribution of PMs was mainly in the range of 2.364 (d10)-26.212 μm (d90) and its median diameter (d50) was 9.996 μm. The sorting factor of the PMs was 1.81 (Eq. (1)), indicating exceptional particle sorting referring to the Trask standard.where d10, d25, d50, d75 and d90 were the particle diameter (μm) of 10%, 25%, 50%, 75% and 90%,
Conclusion
In this work, the micron-sized PMs were synthesized for chemical EOR and relevant physical properties, including morphology, particle size distribution, saline and thermal stability, particle elasticity, etc., were characterized. Additionally, the migration and adsorption behaviors of PMs were comprehensively examined. The conclusions drawn were as follows:
- (1)
The micron-sized PMs prepared by inverse emulsion polymerization possessed superior dispersibility, swelling ability, elasticity, tolerance
Acknowledgments
This research is supported by the National Key Basic Research Program of China (2015CB250904) and the Youth Science and Technology Innovation Team of SWPU (2017CXTD04). The suppliers of the brine samples and the anonymous reviewers are also sincerely thanked. The authors also thank the anonymous reviewers for their valuable comments.
References (36)
- et al.
Formation of colloidal dispersion gels from aqueous polyacrylamide solutions
Colloids Surf, A
(2008) - et al.
Study of deep profile control and oil displacement technologies with nanoscale polymer microspheres
J Colloid Interface Sci
(2014) - et al.
Study on plugging performance of cross-linked polymer microspheres with reservoir pores
J Pet Sci Technol
(2013) - et al.
Conformation and plugging properties of crosslinked polymer microspheres for profile control
Colloids Surf, A
(2015) - et al.
Research and application of micron-size polyacrylamide elastic microspheres (MPEMs) as a smart sweep improvement and profile modification agent
SPE Improved Oil Recovery Conference
(2016) - et al.
Field and lab experience with a successful preformed particle gel conformance control technology
SPE Production and Operations Symposium
(2013) - et al.
Experimental study of the gelation behavior of a polyacrylamide/aluminum citrate colloidal-dispersion gel system
SPE J
(1998) - et al.
Propagation of colloidal dispersion gels (CDG) in laboratory corefloods
SPE Improved Oil Recovery Symposium
(2010) - et al.
Case study on preformed particle gel for in-depth fluid diversion
SPE Symposium on Improved Oil Recovery
(2008) - et al.
Preformed particle gel for conformance control: transport mechanism through porous media
SPE/DOE Symposium on Improved Oil Recovery
(2004)
Modeling particle gel propagation in porous media
SPE Annual Technical Conference and Exhibition
Preformed particle gel for conformance control: transport mechanism through porous media
SPE Reserv Eval Eng
Development of a novel waterflood conformance control system
SPE/DOE Symposium on Improved Oil Recovery
Development and use of a simulation model for mobility/conformance control using a pH-sensitive polymer
SPE Annual Technical Conference and Exhibition
Use of a pH sensitive polymer for conformance control
International Symposium and Exhibition on Formation Damage Control
Preformed-particle-gel extrusion through open conduits during conformance-control treatments
SPE J
Experimental study of gel particles transport through porous media
SPE Latin America and Caribbean Petroleum Engineering Conference
Experimental investigation and correlation of treatment in weak and high-permeability formations by use of gel particles
SPE Prod Oper
Cited by (68)
Synthesis of amphiphilic Janus SiO<inf>2</inf>/styrene butyl acrylate polymer microspheres and their application in oil recovery
2023, Colloids and Surfaces A: Physicochemical and Engineering AspectsMicro-nano polymer microspheres as a plugging agent in oil-based drilling fluid
2023, Colloids and Surfaces A: Physicochemical and Engineering Aspects