Abstract: Rapidly pulsed injection fracture acidizing. A method comprises rapidly pulsed injection of a high reactivity fracture treatment fluid mode or substage alternated with one or more low reactivity treatment fluid modes or substages.

Abstract: In a method of treating a sandstone-containing formation penetrated by a wellbore, a treatment fluid comprising an aqueous fluid containing a Bronsted acid, a hydrogen fluoride source and an organic acid or salt thereof that is substantially soluble in the aqueous fluid is formed. The treatment fluid contains less than about 2% of fluoride (F?) by weight of the fluid and from 2% or less of sodium (Na+) by weight of the fluid. The treatment fluid is introduced into the formation through the wellbore as a single-stage without introducing an acid-containing fluid preflush into the formation prior to introducing the treatment fluid.

Abstract: In a method of treating a sandstone-containing formation penetrated by a wellbore, a treatment fluid comprising an aqueous fluid containing a Bronsted acid, a hydrogen fluoride source and an organic acid or salt thereof that is substantially soluble in the aqueous fluid is formed. The treatment fluid contains less than about 2% of fluoride (F?) by weight of the fluid and from 2% or less of sodium (Na+) by weight of the fluid. The treatment fluid is introduced into the formation through the wellbore as a single-stage without introducing an acid-containing fluid preflush into the formation prior to introducing the treatment fluid.

Abstract: In a method of treating a sandstone-containing formation penetrated by a wellbore, a treatment fluid comprising an aqueous fluid containing a Bronsted acid, a hydrogen fluoride source and an organic acid or salt thereof that is substantially soluble in the aqueous fluid is formed. The treatment fluid contains less than about 2% of fluoride (F?) by weight of the fluid and from 2% or less of sodium (Na+) by weight of the fluid. The treatment fluid is introduced into the formation through the wellbore as a single-stage without introducing an acid-containing fluid preflush into the formation prior to introducing the treatment fluid.

Abstract: In a method of treating a sandstone-containing formation penetrated by a wellbore, a treatment fluid comprising an aqueous fluid containing a Bronsted acid, a hydrogen fluoride source and an organic acid or salt thereof that is substantially soluble in the aqueous fluid is formed. The treatment fluid contains less than about 2% of fluoride (F?) by weight of the fluid and from 2% or less of sodium (Na+) by weight of the fluid. The treatment fluid is introduced into the formation through the wellbore as a single-stage without introducing an acid-containing fluid preflush into the formation prior to introducing the treatment fluid.

Abstract: Methods and systems for investigating downhole conditions are described. One method comprises inserting a tubular into a wellbore, the tubular comprising a tubular section having upper and lower fluid injection ports, and having a thermally insulated fiber optic cable section positioned inside the tubular extending to the upper fluid injection port, and a non-insulated fiber optic cable section positioned outside of the tubular section and extending at least between the upper and lower fluid injection ports; positioning the tubular section having upper and lower fluid injection ports near a suspected thief or pay zone; injecting a fluid through the upper fluid injection port; determining a first differential temperature profile between the upper and lower fluid injection ports; injecting a fluid through the lower fluid injection port; and determining a second differential temperature profile at least between the upper and lower fluid injection ports.

Abstract: Methods and systems for investigating downhole conditions are described. One method comprises inserting a tubular into a wellbore, the tubular comprising a tubular section having upper and lower fluid injection ports, and having a thermally insulated fiber optic cable section positioned inside the tubular extending to the upper fluid injection port, and a non-insulated fiber optic cable section positioned outside of the tubular section and extending at least between the upper and lower fluid injection ports; positioning the tubular section having upper and lower fluid injection ports near a suspected thief or pay zone; injecting a fluid through the upper fluid injection port; determining a first differential temperature profile between the upper and lower fluid injection ports; injecting a fluid through the lower fluid injection port; and determining a second differential temperature profile at least between the upper and lower fluid injection ports.

Abstract: 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.

Abstract: A CO2-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 CO2 on the gelling process.

Abstract: In the horizontal parts of deviated wells arranged within a producing formation, good communication between the formation and the wellbore liner is required, and this may be achieved by using a slotted or perforated liner in the horizontal section without any cementing to bond the liner to the wellbore. However, problems can arise if it is desired to work selectively in a zone in the horizontal section, since with a perforate liner there is no way of isolating the zone from the remainder of the well by using internal packers. This problem can be overcome by providing packers around the outside of the liner, this then allows packers inside the liner to be used to isolate a portion of the well. However, these external casing packers must be sealed against the wellbore, they must be positioned in advance, and they substantially increase the cost of the completion.

Abstract: 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.