Solids Free Completion Fluids Maintain Formation Permeability
Authors: Paul James R. , Plonka James H. 
Published: December 2007

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

During well completions and workovers, it has proven desirable to equalize the pressure of the formations. Minimum fluid movement in the well bore is sought. To accomplish this, fluid is placed in the well of such density to control the reservoir pressure. For safety purposes and to aid certain completion techniques, a slight positive differential pressure into the formation is desirable.

To obtain the needed densities, solutions of sodium chloride, calcium chloride and zinc chloride, and slurries of calcium carbonate and other solids suspensions have been used. Salt water is economical but is limited to about 10 pounds per gallon maximum density. pounds per gallon maximum density. Calcium chloride when inhibited properly is satisfactory to about 11.6 pounds per gallon. Calcium carbonate has limited solubility in water. other insolubles are used for higher densities. Sometimes the fluid viscosity is raised and the fluid loss is lowered to attempt better control.

A new chemical formulation — calcium bromide/calcium chloride — has been used successfully with advantages over all previous materials. It provides a high density clear liquid for provides a high density clear liquid for well completion fluids. Formulations of calcium bromide/calcium chloride can be economically made to weights of 15 pounds per gallon. per gallon. It has been shown that suspended solids frequently can be detrimental in well completions. Both laboratory and field tests indicate that permeability can be reduced or destroyed by perforating or working in fluids containing perforating or working in fluids containing suspended solids. often gas or oil production is difficult or impossible production is difficult or impossible to regain.

Commonly used drilling muds use insoluble solids as weighting materials. During perforating, sand consolidation operations, or other completion procedures, these materials are exposed to procedures, these materials are exposed to the formation. Frequently, some of the fluid in the well bore is injected or lost to the formation. The suspended solids are filtered by the reservoir matrix. This operation can and has decreased the permeability. Wells have been plugged and production lost.

In recent years, deeper, higher pressure wells have resulted in a need pressure wells have resulted in a need for improved completion fluid. This is particularly true of wells in the Gulf particularly true of wells in the Gulf off-shore Louisiana, for example.