Experimental Study of Miscible Thickened Natural Gas Injection for Enhanced Oil Recovery

Abstract

Hydrocarbon-miscible gas flooding typically involves injection of an associated gas (AG) mixture containing mainly methane (CH 4 ) enriched with light hydrocarbon fractions and possibly acid gases. The AG mixture has been recognized as an excellent candidate for miscible gas injection (MGI). However, in general, the viscosity of the AG at reservoir conditions is significantly lower than that of crude oil leading to an unfavorable mobility ratio and low volumetric sweep efficiency during flooding. This study assesses the suitability of a library of commercially available polymers to thicken AG as a means of mobility control. The focus of the study is on the Field A located in the Harweel cluster in southern Oman. First, soluble polymeric thickeners for an AG mixture (CH 4 60%, C 2 H 6 9%, C 3 H 8 6%, and CO 2 25%) were identified using a parallel gravimetric extraction technique combined with cloud point measurements. Then, the viscosity of the identified soluble polymeric candidates in AG mixture was measured in a capillary viscometer at reservoir conditions. Three polymers were found to be completely or partially soluble in the AG mixture at 377 K and 55 MPa including poly(1-decene) (P-1-D), poly(methyl hydro siloxane) (PMHS), and poly(dimethylsiloxane) (PDMS). P-1-D found to be an effective thickener in AG mixture under conditions relevant to Field A, i.e., high temperatures and pressures. The polymer is soluble in the concentration range of 1.5−9 wt%. The viscosity of the P-1-D-thickened AG mixture increased by 2.2−7.4 times greater than AG mixture viscosity at 358−377 K. Furthermore, reservoir condition core flooding experiments were performed to examine the effectiveness of P-1-D-thickened AG gas mixture flooding to enhance oil recovery. The thickened-AG mixture flooding resulted in delayed gas breakthrough and subsequently 10−12% additional oil recovery.

Nano-fluid viscosity screening and study of in situ foam pressure buildup at high-temperature high-pressure conditions

“…The severe cases of unfavorable mobility ratios may lead to early water (chemical) or gas breakthrough to production wells (Agi et al 2018;Al Hinai 2017). High reservoir conditions such as high temperature in most cases contribute to these aforementioned factors, because the viscosity of the injected fluids decreases tremendously with temperature causing fingering to oil bank.…”

CO2 mobility control by small molecule thickeners during secondary and tertiary enhanced oil recovery

“…However, if the miscible PDMS‐CO 2 thickener scenario is considered at the beginning of the reservoir life, it can be more effective than other scenarios. [ 16 ] In addition, the JBN technique was used to obtain the gas/oil relative permeability. The PDMS thickener provides the miscible conditions during the coreflooding scenarios.…”

“…Lee et al [ 17 ] illustrated that the small molecule thickeners of hydroxy aluminium soap and tri‐alkyl‐tin fluoride significantly enhances the viscosity of propane and butane 6‐10‐fold compared to the cross‐linked phosphate ester mixtures. Alhinai et al [ 16 ] used the poly 1‐decene (P‐1‐D), PDMS, and (polymethylhydrosiloxane) PMHS as small molecule thickeners for miscible thickened natural gas flooding. Also, a hydrocarbon gas mixture containing methane (60%), ethane (9%), propane (6%), and carbon dioxide (25%) was considered as an injection gas at reservoir conditions.…”

“…[ 8–14 ] Consequently, in recent decades, experimental and theoretical research has been conducted toward improving gas mobility control by polymer thickeners for gas‐based enhanced oil recovery (EOR). [ 15–18 ] There are two strategies for improving gas mobility control by polymer thickeners: the dissolution of ultra‐high molecular weight polymers into gases, and the dissolution of small molecules as direct thickeners, which both lead to viscosity enhancement. Polymers as direct thickeners for gas mobility control were first used by Heller et al [ 19 ] They indicated that oil‐soluble polymers or nonpolar organic polymers are more effective when dissolved in carbon dioxide than water‐soluble polymers.…”

Direct Gas Thickener

“…Most previous studies, reported that for low/high molecular weight polymers, a concentration of 1.5-7 wt% is required to thicken CO 2 albeit at very high pressure [6]. In recent studies, [16,17] P-1-D has been found to have sufficient solubility in both CO 2 and associated gas (AG) mixtures (at temperatures above 358 K and pressures of 50-55 MPa) to considerably increase gas viscosity. The viscosity enhancement of P-1-D in an AG mixture (25 mol% CO 2 ) and CO 2 was measured in a capillary viscometer at different pressures (50-55 MPa), 377 K, and varying P-1-D concentrations (1.5-9 wt%).…”