Novel Workover Treatment Proves Effective in Permian Basin: Laboratory and Field Results
- S.D. Harms (Welchem Inc.) | J.M. Smith (Welchem Inc.) | G.E. King (Amoco Production Co.) | K. Posey (Welchem Inc.)
- Document ID
- Society of Petroleum Engineers
- Permian Basin Oil and Gas Recovery Conference, 10-11 March, Midland, Texas
- Publication Date
- Document Type
- Conference Paper
- 1988. Society of Petroleum Engineers
- 1.10 Drilling Equipment, 4.1.2 Separation and Treating, 4.2.3 Materials and Corrosion, 4.3.4 Scale, 5.2 Reservoir Fluid Dynamics, 3.2.4 Acidising, 1.6.9 Coring, Fishing, 2.2.3 Fluid Loss Control, 4.5 Offshore Facilities and Subsea Systems, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control, 3 Production and Well Operations, 1.8 Formation Damage, 2.5.2 Fracturing Materials (Fluids, Proppant), 2.4.5 Gravel pack design & evaluation, 6.5.2 Water use, produced water discharge and disposal, 2.2.2 Perforating
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A novel foamed acid treatment has proven effective in the workover of more than 20 wells in the Permian Basin Delaware, Grayburg, and Upper Clearfork formations. The treatment described uses a foaming mutual solvent/acid system. This system provides the desirable wetting and solubilization properties of a mutual solvent and acid along with the inherent advantages of foam. The uniqueness of this treatment is derived from the prolonged stability of the foam, a property not characteristic of foamed mutual solvent systems.
Data is presented from both laboratory and field tests comparing this procedure to conventional foamed acid techniques. Detailed treatment designs are presented which are applicable in coiled tubing and workover strings. These procedures have been used in treatment of injection and producing wells. The treatment described is especially effective in low pressure wells where previous workovers have resulted in poor performance.
For over 20 years, foam has been used in the production of oil and gas. Foam is used in all phases of oil recovery including drilling, stimulation (acidizing and fracturing) and in secondary and tertiary recovery operations. Foam also finds use for diverting during workover, stimulation, enhanced recovery and completions (gravel packing).
The initial attraction to foam for drilling and wellbore cleanout was due to its usefulness in low pressure situations. The good mechanical properties of foam:
1. low hydrostatic head, 2. ability to support fines, 3. low leak-off rates, and 4. shear thinning rheological behavior,
made it an ideal fluid for completion of low pressure gas zones and fracturing low permeability formations. These properties, plus low liquid content and energized fluid return facilitated the use of foam in water sensitive formations. All of these benefits have made foam a common treatment fluid.
Similarly, the benefits of mutual solvents are well known and well documented. In acidizing, these chemicals are used to reduce surface tension which improves acid penetration and promotes cleanup. Due to the "mutual solubility" of these materials, they are effective in penetrating and removing oily coatings on acid-soluble material. This provides for more complete acid spending, thus a more cost-effective job. The surface tension reduction properties of a mutual solvent also assist in removal of water blocks. Some mutual solvents are effective in reducing the possibility of forming an emulsion during acidizing. The use of mutual solvents is also advocated to aid in solubilization of other fluid additives and prevent their adsorption onto the formation. The exact mechanism and the extent to which any given mutual solvent performs any of these tasks is a subject of discussion and experimentation. However, their usefulness as a group is accepted, and depending on the exact application, one mutual solvent might be more suitable than another.
A foamed acidizing system including a mutual solvent is not new, and foaming solvents have been in use for several years.
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