Effect of Rheology on Gel Placement
- R.S. Seright (New Mexico Petroleum Recovery Research Center)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- May 1991
- Document Type
- Journal Paper
- 212 - 218
- 1991. Society of Petroleum Engineers
- 5.2.2 Fluid Modeling, Equations of State, 5.1 Reservoir Characterisation, 1.2.3 Rock properties, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 4.1.2 Separation and Treating, 5.2 Reservoir Fluid Dynamics, 1.6.9 Coring, Fishing, 5.4.10 Microbial Methods
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This study investigates whether rheology can be exploited to eliminate theneed for zone isolation during gel placement. Eight different rheologicalmodels were used to represent the properties existing non-Newtonian gellingagents. Gel placement was examined in linear and radial parallel corefloods andin fractured and in fractured injection wells. The analysis indicates that,compared with water-like gelling agents, existing non-Newtonian gelling agentswin not reduce me need for zone isolation during gel placement in radial-flowsystems.
Near-wellbore gel treatments in injection wells are intended to blockfractures or high-permeability zones so that fluids injected after the geltreatment are more likely to enter and displace oil from other strata.
In most cases, when gelling agents are injected to alter flow profiles in awell, zones are not isolated and the chemicals have profiles in a well, zonesare not isolated and the chemicals have access to all open intervals. Ofcourse, much of the gelant formulation will enter fractures and/orhigh-permeability streaks. Some of this fluid, however, can enter and damageless-permeable, hydrocarbonbearing strata. Recent investigations focused on howflow profiles are modified by unrestricted injection of Newtonian gellingprofiles are modified by unrestricted injection of Newtonian gelling agents.These studies indicate that zone isolation is much more likely to be neededduring gel placement in unfractured wells than in fractured wells. Productivezones in unfractured wells can be seriously damaged if zones are not isolatedduring gel placement.
These studies do not suggest that zone isolation is a cure-all during geltreatments. Clearly, mechanical isolation of zones is not feasible in many(perhaps most) cases. Also, zone isolation is of little benefit if extensivecrossflow can occur between layers or if flow behind pipe can occur. Rather,our analyses are intended to aid in assessing how and where gel treatments arebest applied.
The fundamental question addressed in this paper asks whether gelling-agentrheology can be exploited to eliminate the need for zone isolation during gelplacement.
Numerical methods are used to examine how flow profiles are modified withnon-Newtonian gelling agents. First, rheological models are summarized for flowof existing polymeric fluids in porous media. Then, these models are applied tocalculate the degree porous media. Then, these models are applied to calculatethe degree of penetration during unrestricted injection of gelling agent intovarious two-layer systems. These systems include linear and radial parallelcorefloods and fractured and unfractured injection wells. parallel corefloodsand fractured and unfractured injection wells. In this paper, the terms"gelling agent" and "gelant" refer to the liquid formulationbefore gelation.
Rheological Models for Existing Polymeric Fluids
Eight different rheological models were used to represent the properties ofexisting non-Newtonian gelling agents. Five shear-thinning properties ofexisting non-Newtonian gelling agents. Five shear-thinning models and threeshear-thickening models are included. Figs. 1 through 5 illustrate therheological behavior predicted by five of the models in 100- and 1,000-md rock.The other three models are illustrated in Ref. 4.
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