Water Shut-off Polymer Systems: Design and Efficiency Evaluation based on Experimental Studies

Abstract

Water production control is a key issue in most mature reservoirs worldwide. Many techniques have been developed to achieve this purpose. Water Shut-off (WSO) treatments using crosslinked gels have proven to be an effective alternative. When appropriately designed and applied, these systems generate flow restrictions in high permeable or fractured formations that bypass water from highly saturated zones (injection water or natural brines). WSO treatments efficiency depends on several aspects as reservoir fluids flow patterns, rock petrophysics, formation heterogeneity, and WSO gel characteristics. This last aspect is adjusted to optimize the treatment based on experimental tests performed in the laboratory. This paper presents an experimental methodology to evaluate and adjust WSO polymer systems according to operational and treatment performance requirements. These studies go from qualitative gel consistency and fluid compatibility bottle tests, to rheological characterizations to determine viscosity variations and gelation time (outside porous media tests), as well as flow tests performed on formation and Berea core plugs at reservoir conditions (inside porous media tests). These properties are highly important to avoid early gelations and, at the same time, assure the appropriate WSO placement in the reservoir. Viscoelastic properties such as G* (complex modulus), G′ (storage modulus) and G″ (loss modulus) define the gel strength and provide structural information such as crosslinking density. These parameters are essential to design the gel formulations (polymer and crosslinker type and concentration) depending on the operational and reservoir requirements. Finally, the flow tests performed on core plugs show the changes in water and oil permeability after injecting the treatment. This information is used to calculate the residual resistance factors to water (RRFw), oil (RRFo) and the gel resistance index (GRI). These parameters define the treatment blockage degree and allow estimate probable well production response as well as the best production regimes to extend the treatment life time. This methodology was applied on a new WSO gel system, developed for a wide range of applications. The effect of polymer concentration, temperature, salinity and flow rate are examined in detail. Experimental tests are many times underestimated when planning a WSO job; however these tests will always provide valuable information that will increase the chances of successful water shut-off treatments. The connection between laboratory and field parameters and its influence in the oil and water productivity were analyzed.

Polymer Systems for Water Shutoff and Profile Modification: A Review Over the Last Decade

“…Bailey et al (2000) reported the same figure for 2000. The mechanical methods include the application of particular completion tools, casing replacement, or separation of produced water by use of hydrocyclones (Vega et al 2010). The disposal of produced water seriously affects the environment, especially if the produced water contains mercury, arsenic, and other salts (Hibbeler and Rae 2005).…”

Development of a novel water shut‐off test method: Experimental study of polymer gel in porous media with radial flow

“…Most the polymer gel studies have discussed gel characterization and rheology specifications . To our knowledge, few studies have been conducted on the usage of polymer gel methods, and the reported data are limited to theoretical discussion and simulation …”

“…Then water permeability reduction was nearly 94 %. With changing PAM concentration, RRF W (water residual resistance factor) varied < 10 and > 10 000 in the sandstone with permeability of about 0.493 (μm) 2 (500 mD) …”

“…As mentioned before, the use of polymer gel treatment for fractures and reservoirs with linear flow is quite common . However, there are numerous challenges for which few investigations have been developed, including a) reservoirs with radial flow, b) reservoirs with low permeability, and c) wells without oil zone protection . Despite the successful application of polymer gels in controlling water in reservoirs with linear flow and high permeability, some of them have been reported to be ineffective on field trials .…”

Swelling and Deswelling Kinetics of AT-O3S Polymer

“…Among these gel systems using both polyacrylamides and different crosslinkers have been the most extensively applied [13]. These crosslinkers can be classified as either inorganic or organic [14].…”