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Development of formation damage models for oilfield polymers.

Idahosa, Patrick Egbe Goddey


Patrick Egbe Goddey Idahosa


Babs M. Oyeneyin


Polymers are among the most important of various oilfield chemicals and are used for a variety of applications in the oil and gas industry (OGI), including: water and gas shutoff; drilling mud viscosity modification; filtration loss control (FLC); swellable packers; loss circulation material (LCM) pills; enhanced oil recovery (EOR); fracture treatment and cleanup; and chemical placement. The deposition and retention of polymer molecules in porous media, and their interactions with rock and fluids present complex phenomena that can induce formation damage. Formation damage due to polymer retention can occur via mobility reduction in three possible mechanisms of polymer-induced formation damage: 1) pore-throat blocking, 2) wettability alteration (which can alter permeability), and 3) increase in reservoir fluid viscosity. Physical adsorption can also cause permanent permeability impairment (formation damage). This polymer-induced formation damage causes a reduction in net oil recovery and continues to be a fundamental problem in the industry. This is due to the rather shallow understanding of the mechanics of polymer-brine-rock interactions and the polymer-aided formation damage mechanisms. Most models available for polymer risk assessments appear to be utilised for all scenarios with unsatisfying results. For example, very little is known on how polymer type - particularly in the presence of brine type - impacts on formation damage. In order words, one of industry's current challenges is finding effective polymers for high-salinity environments. Additionally, the effects of polymer charge and charges at the brine-rock interface are other issues that require a deeper understanding in order to address the role polymers play in formation damage. Furthermore, there has been no real recognition given to polymer rheological behaviour (in complex porous media, etc.). The OGI therefore still faces the challenge of an inability to correctly predict hydrolysed polyacrylamide (HPAM) viscosity under shear degradation, and consequently have not been able to meet the need of production predictions. The effects of the above-mentioned factors have not been fully integrated into polymer formation damage modelling. In this thesis, analytical methods were used alongside theoretical, numerical, and laboratory experiments to further investigate the mechanics of polymer-brine-rock interactions, and to establish the mechanisms for formation damage related to polymer application. Three different hydrolysed polyacrylamide (HPAM) products (SNF FP3630 S, 3330 S and FloComb C3525) were used in the experiments, while Xanthan gum was used in the simulation work. The following variables were considered: 1) polymer type, 2) effect of concentration, 3) effect of salinity/hardness, 4) effect of permeability and pore size distributions, 5) effect of inaccessible pore volume (IAPV) on retention, 6) effect of flow rate (where a special method was established to quantify the effect of flow rate on polymer retention). Laboratory rheological and adsorption experiments were designed and conducted. Experimental results indicate that a higher concentration of calcium divalent ions in brine help to promote polymer retention on the rock surface. On the basis of the experimental results, empirical models were developed and validated in order to predict HPAM rheological behaviour over a wide range of shear rates and also to predict salinity-dependent polymer-induced formation damage. Additionally, the thesis proposes a modified screening model that can aid polymer selection for field application design. Overall, these models can therefore serve as useful tools for quick prediction and evaluation of polymer related formation damage in oil and gas-bearing formations.


IDAHOSA, P.E.G. 2015. Development of formation damage models for oilfield polymers. Robert Gordon University, PhD thesis.

Thesis Type Thesis
Deposit Date Jul 16, 2019
Publicly Available Date Jul 16, 2019
Keywords Polymer applications; Formation damage; Oilfield chemicals; Oil and gas industry
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