Wettability and fluid displacement in a well

Abstract

An inverter fluid that intermixes with a non-aqueous (e.g., oil) external / aqueous internal fluid to cause external / internal inversion is designed. This includes testing a selected inverter fluid with a test fluid having a composition nominally equivalent to the composition of the non-aqueous external / aqueous internal fluid. A quantity of the designed inverter fluid is made and placed in the annulus of a well, such as an oil or gas well, to remove the non-aqueous external / aqueous internal fluid on at least a portion of one or more surfaces of the annulus. This can include pumping the inverter fluid along with a stream of cement. The inverter fluid displaces at least part of the non-aqueous external / aqueous internal fluid in the annular region and inverts the coating of non-aqueous external / aqueous internal fluid sufficient to remove the coating ahead of the cement. Determining a suitable inverter fluid comprises: measuring a parameter related to electrical conductivity of an initial mixture including (1) a test fluid having a composition nominally equivalent to the non-aqueous external / aqueous internal fluid and (2) part of a selected inverter fluid; and adding a further part of the selected inverter fluid to the initial mixture until the measured parameter indicates the external / internal phases of the test fluid have inverted.

Description

BACKGROUND OF THE INVENTIONThis invention relates generally to displacing fluids and water-wetting surfaces within a well, such as an oil or gas well. In one specific example, the present invention facilitates proper bonding of cement to side surfaces of an annulus in the well in which the cement is placed. This includes determining suitable displacement fluids that sufficiently wet the sides of the annulus to enable proper cement bonding. The present invention has applicability other than cementing, but in such other applications it still pertains to wettability and determining compositions for achieving suitable water-wetting within an oil or gas well.In one manner of drilling a well, "drilling mud" is pumped into a rotated drill string to which a drill bit is attached. The mud typically exits through openings in the drill bit to lubricate the bit and to carry cuttings up an annulus between the drill string and the wellbore for disposal at the surface. One type of drilling mud is ...

AI Technical Summary

Benefits of technology

In specific implementations, this invention is particularly applicable to wettability evaluation of spacers or preflushes suitable to water-wet downhole surfaces to which cement is expected to bond during a well cementing operation performed after the well has been drilled using oil or synthetic-based drilling fluids, for example. The present invention can improve the effectiveness of a cementing job in a well while making economical and efficient use of materials used in the job. In general, the present invention provides a convenient means of evaluating new materials for the purposes of inverting oleaginous external phase drilling fluids and imparting water-wetting of the downhole surfaces.

Problems solved by technology

Bonding of the cement to the tubular string or to the wellbore surface can be less than desirable if the string and wellbore surfaces are not conducive to cement bonding.

Formation of a micro-annulus can lead to undesirable fluid migration outside the wellbore casing, thus losing zonal isolation of the wellbore.

Further, casing lifetime may be compromised if migrating fluids are corrosive.

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