Diverting agents

Laboratory studies of foam flow in porous media suggest that the relative foam mobility is approximately inversely proportional to the permeability. This means that foam has potential as a flow-diverting agent, in principle sweeping low-permeability regions as effectively as high-permeability regions [716]. 

Diverting agents assist in distributing acid more uniformly through the perforated formation interval (141). These are usually oil-soluble hydrocarbon resin particles. They may be dissolved by post-acid injection of xylene or similar solvents. Oil-soluble waxes, naphthalene, and solid organic acids such as benzoic acid have also been used (142). Best results are obtained using a broad range of particle sizes. 

CMHEC 2 32 3 C N.S. N.S. RF Fluid loss additive and retarder for cementing, spacers, gelling weak acids, temporary diverting agents in fracturing (crosslinked gels)... 

Hill, O.F., Ward, A.J., and Clement, C.C. "Austin Chalk Fracturing Design Using a Crosslinked Natural Polymer as a Diverting Agent," J. Pet. Technol.. 1978, 30(12), 1795 804. 

In recent years there has been considerable interest in the use of foams in chemical steam flood, CO2, and low tension processes. To date, principal applications have been as diverting agents where the foam has been used to block high permeability, low oil saturation zones and hence force drive fluids through lower permeability, higher oil saturation zones. The utility of foams in more general mobility control roles has not been extensively... 

Petroleum production from subterranean reservoirs can be increased by injecting water as liquid or steam. Various chemicals have been added to the water or steam to increase volumetric sweep efficiency. One alternative is the use of emulsions which serve as diverting agents to correct the override and channeling problems that occur during fluid injection. Laboratory results show that it may be possible to control channeling and steam override with an emulsion blocking technique. The emulsion can be formed with the aid of a surfactant mixture or by use of natural surfactants that exist in some crude oils. Core-... 

Long Beach CO2 Diversion Test(4). The injection of an 85 15 mixture of CO2 and N2 into the Tar Zone of Fault Block V of the Wilmington, California, field began in February 1982, after the field had been water flooded for 20 years. The field pressure (1,100 psi) was well below the miscibility pressure (> 3,000 psi) of the heavy (14 API gravity) oil. In this 320 acre WAG project gas was injected in 2 wells and water in 8, with the gas injection rotated among the 10 injection wells. One of these 10 wells was selected as the injector for a test of the surfactant Alipal CD-128 as a diverting agent. 

Many of these formations consist of layers of porous media with varying permeability. If a zone is very permeable relative to the rest of the formation, most of the injected fluids will enter it. Extremely viscous CO2 could be used as a diverting agent which would tend to minimize flow through a highly permeable layer. In this application a gel or very viscous liquid would be formed near the wellbore in this layer and remain immobile. Subsequently injected fluids would then flow into the other layers. 

Investigations (34, 35) to study the effects and limitations of brine and acid foams as diverting agents for nonfoamed acids developed several interesting conclusions. In several case studies of actual stimulated wells... 

NAVRATIL, M., SOVAK, M. and MITCHELL, M. S., Diverting Agents for Sweep Improvements in Flooding Operations - Laboratory Studies, SPE 10621, presented at SPE Int. Symp. on Oilfield and Geothermal Chemistry, Dallas, Texas, January 1982. 

The application of gels in subterranean oil bearing formations as diverting agents for the flow of driving fluids is widely reported > It is not within the scope of this paper to... 

S. S. Nagra, J. P. Batycky, R. E. Nleman, and J. B. Bodeux, Stability of Waterflood Diverting Agents at Elevated Temperatures In Reservoir Brines, Paper SPE 15548, presented at the 61st Annual Technical Conference and Exhibition of the SPE, New Orleans, LA, October 5-8 (1986). 

Foams have been tested as diverting agents in waterfloods, 39 as steam-diverting agents to reduce gravity override or steam channeling in steamfloods, and as mobility-control fluids in CO2 displacements. 4 ... 

Duerksen, J.H. Laboratory Study of Foaming Surfactants as Steam Diverting Agents, SPERE (Jan. 1986) 44-52. 

C. Note the pressure response when the diverting agent reaches the formation. The surface pressure should rise slightly. If there is no response, more diverter or a different diverter may be needed in the future. 

Gallus, J. P., and D. S. Pye. 1969. Deformable diverting agent for improved well stimulation. J oarwa / of Petroleum Technology. April 497-504. 

Houchin, L. R., D. D. Dunlap, L. M. Hudson, and P. C. Begnaud. 1986. Evaluation of oil-soluble resin as an acid diverting agent. Paper SPE 15574, presented at the Society of Petroleum Engineers Annual Technical Conference and Exhibition, New Orleans. 

Note the pressure response when the diverting agent reaches the formation. 

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