Electrically conductive oil-based mud
First Claim
1. A drilling fluid comprising a polar base oil and complimentary fatty acid surfactants blended or combined such that the base oil and the surfactants comprise the oil based layer of an invert emulsion, wherein the base oil and the surfactants comprise about 90 volume percent of the emulsion and calcium chloride brine comprises the water phase of the emulsion, wherein said complimentary fatty acid surfactants are selected from the group consisting of sorbitan esters, sorbitan ester derivatives, ethoxylated sorbitan esters, ethoxylated sorbitan ester derivatives, and combinations thereof, and wherein at least one of the complimentary fatty acid surfactants is more water soluble than another and at least one of the complimentary fatty acid surfactants is more oil soluble than another, such that the surfactants form micelles in quantities providing a staggered arrangement and denser concentration in the palisade layer of the drilling fluid than either surfactant would form alone, such that the drilling fluid has sufficient electrical conductivity to facilitate resistance-based wellbore logging while also having utility as an oil-based drilling fluid.
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Abstract
An electrically conductive oil mud meeting the fluid requirements for resistive logging tools and a method for preparing such mud is disclosed. The fluid has been optimized to deliver performance in a manner as similar to that of a traditional invert emulsion drilling fluid as is practical while still maintaining the required electrical conductivity for resistivity-based logging tools. This electrically conductive oil-based mud comprises a polar synthetic ester base and complimentary ester surfactants, one being more oil soluble, the other being more water soluble. The surfactants interact synergistically to provide dense packing of micelles at the palisade layer. This fluid is oil-wetting to solids, and in general behaves like a traditional oil mud.
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Citations
13 Claims
- 1. A drilling fluid comprising a polar base oil and complimentary fatty acid surfactants blended or combined such that the base oil and the surfactants comprise the oil based layer of an invert emulsion, wherein the base oil and the surfactants comprise about 90 volume percent of the emulsion and calcium chloride brine comprises the water phase of the emulsion, wherein said complimentary fatty acid surfactants are selected from the group consisting of sorbitan esters, sorbitan ester derivatives, ethoxylated sorbitan esters, ethoxylated sorbitan ester derivatives, and combinations thereof, and wherein at least one of the complimentary fatty acid surfactants is more water soluble than another and at least one of the complimentary fatty acid surfactants is more oil soluble than another, such that the surfactants form micelles in quantities providing a staggered arrangement and denser concentration in the palisade layer of the drilling fluid than either surfactant would form alone, such that the drilling fluid has sufficient electrical conductivity to facilitate resistance-based wellbore logging while also having utility as an oil-based drilling fluid.
- 2. An electrically conductive drilling fluid comprising a polar ester oil-base, a sorbitan ester derivative surfactant, and an ethoxylated sorbitan ester derivative surfactant, wherein said surfactants are in quantities sufficient to create micelles having enhanced concentration in the palisade layer, and wherein said polar ester oil-base comprises a monocarboxylic acid ester of a C2 to C12 monofunctional alkanol.
Specification