Elsevier

Fuel

Volume 235, 1 January 2019, Pages 249-258
Fuel

Full Length Article
A comprehensive investigation of polymer microspheres (PMs) migration in porous media: EOR implication

https://doi.org/10.1016/j.fuel.2018.07.125Get rights and content

Highlights

  • Micron-sized PMs were synthesized and relevant physical properties were characterized.

  • The SEM micrographs of the micro-pores plugged by PMs were presented.

  • The matching relationship between PMs and pore throats was established via matching coefficients introduced.

  • The effect of particle elasticity on migration of PMs was involved.

  • The adsorption and desorption behaviors of PMs were assessed.

Abstract

A type of polymer microspheres (PMs) with superior dispersity, swelling, elasticity, and saline and temperature resistance was prepared in this work through inverse emulsion polymerization. It was observed that these PMs experienced elastic deformation and obstructed micro-pores by means of complete, single and bridge plugging, and thus causing additional flow resistance. The migration modes of the PMs in porous media could be defined as smooth pass, elastic plugging-remigration incorporating low-efficiency and high-efficiency plugging, and complete plugging, on the basis of matching coefficients between the PMs and pore geometry. The plugging capability of the PMs was largely dependent on the matching coefficients. Interestingly, it was found that if appropriate matching coefficients was obtained, the PMs with higher elastic modulus showed an enhanced plugging capability even with smaller particle size. In addition, the results of adsorption and desorption behaviors of the PMs implied that the adsorbed PMs partially detached as a result of caused flow fluctuation and decline/disappearance of secondary adsorption potential well. It is believed that the proposed PMs could be a viable, robust and promising candidate for conformance control and oil recovery improvement.

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.S=d75d25where 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)

  • Y.S. Wu et al.

    Modeling particle gel propagation in porous media

    SPE Annual Technical Conference and Exhibition

    (2008)
  • B.J. Bai et al.

    Preformed particle gel for conformance control: transport mechanism through porous media

    SPE Reserv Eval Eng

    (2004)
  • H. Frampton et al.

    Development of a novel waterflood conformance control system

    SPE/DOE Symposium on Improved Oil Recovery

    (2004)
  • I. Benson et al.

    Development and use of a simulation model for mobility/conformance control using a pH-sensitive polymer

    SPE Annual Technical Conference and Exhibition

    (2007)
  • H. Al-Anazi et al.

    Use of a pH sensitive polymer for conformance control

    International Symposium and Exhibition on Formation Damage Control

    (2002)
  • A. Imqam et al.

    Preformed-particle-gel extrusion through open conduits during conformance-control treatments

    SPE J

    (2014)
  • A. Al-Ibadi et al.

    Experimental study of gel particles transport through porous media

    SPE Latin America and Caribbean Petroleum Engineering Conference

    (2012)
  • A. Al-Ibadi et al.

    Experimental investigation and correlation of treatment in weak and high-permeability formations by use of gel particles

    SPE Prod Oper

    (2013)
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