Schlumberger Technology Corporation

Stephen N Davies

Gary John Tustin

Timothy G J Jones

Trevor Lloyd Hughes

Gerald Henry Meeten

Geoffrey Colin Maitland

Paul William Way

Mostafa A Tehrani

Demosthenis Georgeou Pafitis

Francois Friedmann

Silke Olthoff

A method to reduce water influx into a producing well is described comprising the steps of pumping a chemical composition into a production interval and into surrounding formation; said composition being capable of forming, firstly, a physically stabilized structure and, secondly, a chemically stabilized structure, wherein said physically stabilized structure being dissolvable by hydrocarbon containing fluids; letting said composition form said physically stabilized structure within the formation surrounding said production interval; changing pressure condition in said production interval such that the fluid flow within the surrounding formation is reversed; letting thereby in some portions of the formation hydrocarbon containing fluids dissolve said physically stabilized structure and chemically stabilize said structure in the remaining portions by a cross-linking reaction. The time constants of the two stabilizing reactions are selected such that the physical stabilization is essentially completed before the pumping direction is reversed and the chemical stabilization is essentially completed after the pump-out/cleaning operation.

Method for water control

A composition, in particular a wellbore service fluid, comprising monomeric surfactants, preferably viscoelastic surfactants, in combination with a polymerization agent. Additionally, the fluid may contain a cross-linking agent to cross-link the polymerized surfactants.

Surfactant based gelling composition for wellbore service fluids

A settable thixotropic material comprises a thixotrope and a settable substance, the material being capable of gelling reversibly in a gelling time of less than 60 seconds. The thixotrope conveniently comprises a fine grained clay, especially smectite clays, e.g. hectorites. It is preferred to use synthetic smectite type clay colloids, and goods results have been obtained with the synthetic clay known as Laponite RDS. The settable material conveniently comprises cement, particularly Portland cement. The thixotropic material finds use generally in oilwell applications, e.g. to plug lost circulation zones, to repair damaged or corroded casing, as grouts, and to limit annular gas migration. The material also finds particular application in techniques for completion of horizontal wells completed with slotted or pre-drilled liners.

Thixotropic materials

A CO,-foamable gelling composition and use of said composition for conformance control operations are described The gelling fluid comprises a decomposing agent to counteract the detrimental effect of CO,on the gelling process.

Foamable gel composition

A composition and uses of said composition are described for a latex based setting system for remedial and other operations within a wit bore. The composition comprises a pH-reducing agent and/or a coagulant. By controlling the amount of agent, the setting time of the system can be controlled in a range of 0.5 h to 15 h.

Setting composition for well operations

An additive for a water-based fluid which is to be used when the likelihood of differential sticking is high and which reduces the sticking tendency of the fluid and mud cake. An additive according to the invention comprises a well dispersed-particulate phase such as an emulsion, a fine emulsion, a microemulsion, a micellar phase or a polymeric phase having a particle size comparable with the pore throat size of a mud cake and comprising a material which forms easily deformable particles and which reduces the sticking propensity of the mud. One embodiment of the invention comprises a microemulsion of an oil which is well dispersed, substantially stable and has a substantial portion of the particle size distribution in the range 5-500 nm. An alternative embodiment comprises a micellar phase comprising one or more surfactants. The additive is typically used at a level of about 5% by volume in the drilling fluid.

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Stephen N Davies