A Laboratory Study of In-Depth Gel Treatment To Improve Oil Recovery
- Jinxun Wang (Saudi Aramco) | Ammar J. Alshehri (Saudi Aramco) | Abdulkarim M. AlSofi (Saudi Aramco) | Abdullah M. AlBoqmi (Saudi Aramco)
- Document ID
- Society of Petroleum Engineers
- SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, 24-27 April, Dammam, Saudi Arabia
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 4 in the last 30 days
- 95 since 2007
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The extreme heterogeneity of carbonate in the form of fracture corridors and super-permeability thief zones challenges the efficient sweep of oil in both secondary and tertiary recovery operations. In such reservoirs, conformance control is crucial to ensure injected water and any enhanced oil recovery (EOR) chemicals optimally contact the remaining oil with minimal throughput. Gel-based conformance control has been successfully applied on both sandstone and carbonate reservoirs. In-depth conformance control in high temperature reservoirs is still a challenge, due to severe gel syneresis and the associated significant reduction in gelation time.
In this work, a laboratory study was conducted on a polymer/chromium gel system for a high-temperature carbonate reservoir to evaluate the gelant formulation potential for diversion and recovery improvement. We perform four oil displacement experiments on carbonate core samples to demonstrate oil recovery improvement by gel treatment. In these tests, the gel solution was injected into specially prepared heterogeneous carbonate composite core samples, in which different configurations of high permeability channels were created. Gel treatment was conducted after waterflooding and was followed by chase waterflooding while monitoring oil production. Oil recovery improvement by gel treatment was 18% of original oil in core (OOIC) in the composite core with high permeability channels extending mid-way through the composite while the improvement was 38% OOIC in the composite core with channels extending all the way through the composite. This indicates that the high permeability channels were effectively blocked and bypassed oil was successfully mobilized after gel treatment.
This laboratory study provides more insight into the mechanisms of oil-recovery improvement by gel treatment. Moreover, it clearly demonstrates the oil-recovery potential of in-depth gel systems in heterogeneous reservoir applications at high temperatures.
Fractures or high-permeability zones are often observed in carbonate reservoirs, causing channeling of injected fluids towards producers and consequently poor sweep of oil residing in the matrix. Conformance control is crucial in such heterogeneous reservoirs during both waterflooding and enhanced oil recovery (EOR) processes. The poor performance of many earlier EOR projects was attributed to conformance problems (Sydansk and Southwell, 1998). Conformance control is required to ensure EOR chemicals efficiently contact the remaining oil with minimal throughput. Different types of conformance control methods were reviewed by Sydansk and Romero-Zerón (2011). Among chemical conformance methods, polymer gels are widely used due to their relatively low cost and ease of application at well sites. When a gelant solution consisting of a water-soluble polymer and cross-linker(s) is injected, an elastic solid-like gel system will form after a certain time due to elevated reservoir temperatures. As a result, any subsequent injection water will be diverted to the unswept/less-swept regions, leading to an improvement in sweep efficiency.
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