A Simple Technique to Determine the Strength of Millimeter-Sized Particle Gel

Abstract

Millimeter-sized superabsorbent polymers (SAPs), also called preformed particle gels (PPGs), are gaining attention and popularity for use in conformance-improvement treatments. The strength of PPGs is important to the optimization of their performance as plugging agents. Conventional gel strength has always been measured by applying load to single, isolated sample with certain geometry. However, determining the strength of sugar-like PPGs with irregular shapes is a challenging task. Previous publications have proposed different methods to evaluate gel strength. However,those methods are not suitable for rapid quantitative evaluation of PPG strength on site. We designed a simplified experimental apparatus to evaluate gel strength in the laboratory or on site during gel treatment. It consists of a positive displacement hand pump and a specially designed piston accumulator. The top cap of the accumulator has a hole connected to the pump by tubing and fittings. The bottom cap is a stainless steel screen plate with multiple holes. During the experiments, we placed swollen PPG on top of the screen plate and below the piston, gradually increasing the pressure to push the piston until gel particles passed through the plate holes. The minimum pressure needed to push gel particles out of the holes was considered as the threshold pressure of a gel particle moving through a pore throat, which provides quantitative indication of the gel strength. The apparatus also can be used to evaluate gel rheology in terms of its apparent viscosity as a function of the shear rate. We observed that the PPGs are prone to stiffen as the brine salinity increased which caused the threshold pressure to increase. Also the PPGs threshold pressure depended chiefly on the brine salinity, the screen hole size, and the holes density per screen plate. Additionally, the PPGs threshold pressure correlated excellently with their elastic modulus which was measured using a rheometer. PPGs injection pressure did not increase significantly with the injection rate. This behavior is consistent with the real-time injection pressure and injection rate change which has been often observed during PPG treatments in oilfields. This method can serve as a simple, fast, and practical technique to quantitatively evaluate particle gel strength in the laboratory and on site during a PPG treatment process.

Meeting Name

19th SPE Improved Oil Recovery Symposium (2014: Apr. 12-16, Tulsa, OK)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

High Pressure Effects; Oil Fields; Apparent Viscosity; Experimental Apparatus; Injection Pressures; Millimeter-Sized Particles; Positive Displacement; Quantitative Evaluation; Superabsorbent Polymer; Threshold Pressures; Pistons

International Standard Book Number (ISBN)

978-1632663863

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2014 Society of Petroleum Engineers (SPE), All rights reserved.

Publication Date

01 Apr 2014

Link to Full Text

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