Laboratory Evaluation of High-Temperature Conformance olymer Systems

Abstract

This paper presents the results of laboratory evaluation regarding the effectiveness of novel, organically crosslinked, high-temperature, conformance polymer gel systems as sealants. Effectiveness of these sealant gels is evaluated by attempting water flow through high-permeability cores under residual oil conditions. The effectiveness of the sealants toblock water permeability at temperatures up to 350°F,provide long-term sealant properties at these temperatures, andprovide adequate gel time for placement is measured. The ultimate goal is to determine whether the selected crosslinked polymer systems provide useable extended gel times and maintain thermal stability to 350°F. Discussed arethe physical laboratory model and test conditions used to perform dynamic core flow studies over extended periods in determining the impact of sealant exposure to elevated temperatures and subsequent required modifications,experimental procedure used for dynamic core flow studies,the effect of temperature on permeability reduction over time,the impact of threshold pressure (differential pressure required before fluid flow begins through a treated core) on permeability reduction over time,laboratory methodology used for gelation time measurement of a new, novel, organically crosslinked, high-temperature, conformance polymer gel system, andlaboratory results regarding gelation time of the polymer system as a function of temperature up to 350°F. Introduction Excessive water production from hydrocarbon reservoirs is one of the most serious problems in the oil industry. Remediation techniques for controlling water production, generally referred to as conformance control, include the use of polymer systems to reduce or plug permeability to water. This paper mainly discusses water control in high-temperature environments for treating hydrocarbon-producing wells to reduce water production for applications in which water and hydrocarbon zones are clearly separated. The principle of operation of this technique is to pump the polymer system into the formation around the wellbore and then propagate through the rock matrix. In-situ gelation takes place, plugging pore spaces and channels, thereby limiting undesired water flow. Then, a permanent barrier strategically placed only in the water zone is formed because the oil- and water-producing zones can be mechanically isolated. Literature Review A variety of techniques for controlling water production have been attempted by the oil industry. Earlier attempts to reduce water production included mechanical isolation, squeeze cementing, solid slurry (clay) injection, and oil/water emulsion and silicate injection. More successful results have been obtained with in-situ polymerized systems, crosslinked polymeric solutions, and silicate-based gels.1 Polymer gel systems have emerged over the last decade as one of the most effective tools for controlling water production. One of the most widely used polymer systems employs polyacrylamides (PAMs) or acrylamide co-polymer and chromium [Cr(III)] as a crosslinker.2 Cr(III) has been extensively used because of its high success rate and relatively low cost. However, the short gelation times of this system at elevated temperature limit their application to lower temperature reservoirs.3 Other problems with this system include thermal stability, unpredictable gel times, gel instability in the presence of chemical species that are potential ligands, toxicity concerns, and limited propagation into the target pore volume.4 Another polymer system widely used is a water-based gel based on phenol/formaldehyde crosslinker for homo-, co-, and ter-polymer systems containing acrylamide. The loss of phenol by partitioning into the crude oil that it contacts has been identified as an important issue for this polymer system.5 Toxicity issues associated with formaldehyde and phenol need to be overcome as well.

Gelation Kinetics and Performance Evaluation of an Organically Crosslinked Gel at High Temperature and Pressure

“…For example, copolymers of polyacrylamide tert-butyl acrylate (PAtBA) (Morgan et al 1998), mixtures of acrylamide and acrylamido-2-methylpropane sulfonic acid (AMPSA) (Vasquez et al 2003), mixtures of acrylamide, AMPSA and N,N-dimethyl acrylamide (Vasquez et al 2005) can be crosslinked with PEI through covalent bonding. These PEI crosslinked systems have been extensively examined in porous media (Hardy et al 1998;Alqam et al 2001;Zitha et al 2002;Vasquez et al 2003Vasquez et al , 2005.…”

“…In DPR, the relative permeability to water is reduced to a greater extent than that to oil (or gas). Polymer gels were also used to totally block the pore space of the water producing zones in both matrix (Vasquez et al 2003) and fractures (Alqam et al 2001).…”

Flow of a Cross-Linking Polymer in Porous Media

“…The most appropriate chemical system for in-depth profile modification in a reservoir should have the following properties: tolerance to the salinity of the brine, thermal stability, low initial viscosity, deep propagation into a reservoir, and low mechanical degradation (Karsani et al 2014;Zhang and Zhou 2008;Zitha et al 2002). There are a few XL polymers that can meet the desired requirements for profile modification problems in specific reservoir conditions (Sydansk 1988;Vasquez et al 2003;Crespo et al 2014). One of the commonly Fig.…”

DSC investigation of the gelation kinetics of emulsified PAM/PEI system

“…Polymer and polymer gels are well suited to totally block the water production zones [3,4]. The use of & Ibnelwaleed A. Hussein ihussein@kfupm.edu.sa; ihussein@qu.edu.qa polymeric gels reduces the relative permeability of water [5,6] during oil and gas production and improves the sweep efficiency of injection wells [7,8].…”