Fluid-Loss Control Through the Use of a Liquid-Thickened Completion and Workover Brine
- T.E. Hudson (Dowell Div. of Dow Chemical U.S.A.) | M.D. Coffey (Dowell Div. of Dow Chemical U.S.A.) | C.W. Sauer Jr. (Conoco Inc.) | A.S. Teot (Dow Chemical Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- October 1983
- Document Type
- Journal Paper
- 1,776 - 1,782
- 1983. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 2 Well Completion, 2.2.2 Perforating, 4.3.1 Hydrates, 2.7.1 Completion Fluids, 2.4.3 Sand/Solids Control, 2.2.3 Fluid Loss Control, 3 Production and Well Operations, 1.8 Formation Damage
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A new liquid thickening agent has been developed for controlling fluid loss of clear brines. This control is of critical concern during the completion or workover of an oil, gas, or service well.
Many clear brines are expensive (up to $800/bbl for some concentrations). The loss of these fluids to the formation can become a significant completion/workover expense. From a safety standpoint, the loss of clear brines to a formation may create a reduction in hydrostatic pressure, which would increase the potential of a well kick or blowout.
The newly developed agents function in brines with densities from 9.1 to 19.2 lbm/gal. They are superior to the traditionally used polymer because they start to build viscosity instantly, without the formation of "fish eyes." The viscosity developed in the clear brines through the addition of these materials can be broken easily at the surface by the addition of small amounts of commonly available breakers. Brines containing this polymer show little or no permanent return permeability damage. The properties of the materials as fluid-loss-control additives in clear brines, their nondamaging characteristics, and rheological properties of the thickened brines are described. Case histories support the advantages of these properties.
Fluid-loss control of clear brines is of primary concern during the completion or workover stage of an oil, gas, or injection well. The clear brines used in completions and workovers typically contain KCl, NaCl, CaCl2, CaBr2, and ZnBr2, or combinations of these salts, and range in density from 8.4 to 19.2 lbm/gal. These brines cost from a few dollars for the least-dense brine to about $800 for a 19.2-lbm/gal brine. The loss of these relatively high-cost, clear brines to the formation can be of significant importance when attempts are made to minimize completion and workover expenses. Loss of fluid level, resulting in a decrease of hydrostatic pressure on the formation, which exposes the rig and personnel to the danger of a well kick or blowout. Fluid-loss-control mechanisms when clear brines are in use have traditionally included (1) reducing the density of the completion or workover fluid, thereby imposing less hydrostatic pressure on the formation, (2) adding solids such as graded CaCO3 particles, FeCO3 particles, or sized rock salt, and (3) increasing the viscosity of the clear brines by adding dry polymers such as guar gum, hydroxylpropyl guar, xanthan gum, and (most commonly) hydroxyethylcellulose (HEC). These methods have been used independently and in combination with one another.1-4
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