The Application of Novel Wax Divertor Technology to Allow Successful Scale Inhibitor Squeeze Treatment into a Sub Sea Horizontal Well, North Sea Basin

Abstract

This paper presents field results from two scale squeeze treatments carried out on the same sub sea horizontal well from a field in the North Sea, The initial squeeze was a bullhead application of phosphonate scale inhibitor to control a sulphate scale problem in a horizontal well. Ten months after the initial treatment a second bullhead squeeze treatment was applied in two stages. This utilised a thermally degraded pelted wax divertor to temporally impair injectivity in the heel region of the horizontal well thus allowing propagation of the second stage of the squeeze treatment into the mid section of the horizontal well. This paper will show the significance of production logging tool data toevaluate the location of deposited scale and water production prior to a squeeze treatment. Such data was used to design a novel two stage squeeze treatment in which an initial squeeze slug was applied to the heel region followed by application of a pelted thermally degraded wax divertor to prevent further loss of scale inhibitor to the heal region. The action of the divertor allowed a second scale inhibitor to the heel region. The action of the wax divertor allowed a second scale inhibitor slug to be placed further along the horizontal section of the well. Details of divertor selection and the squeeze design strategy implemented in this squeeze treatment will be presented. During the field treatment, physical (downhole pressure and temperature) data and chemical (non-radioactive tracers, inhibitor and ion Concentrations) data were recorded. This data will be used to indicate the success of diversion treatment by comparison with the first squeeze applied to the same well ten months previously. This is the first successful application of a thermally degraded wax divertor to a subsea horizontal well in the North Sea basin. The well was successfully treated with no process up set during flowback and no decline in well production whilst allowing the well bore to be protected from continued sulphate scale formation. This paper clearly shows that with the correct selection of both scale inhibitor, divertor agent together with the utilisation of all available information relating to the reservoir. It is possible to squeeze scale inhibitors into sub-sea horizontal wells without the need for expensive coiled tubing intervention from a diving support vessel. This technology is not limited to horizontal wells and could also be applied tovertical wells with significant cross flow problems to aid in selective placement during scale inhibitor squeezing. P. 633

Selection of Scale Control Strategy on a Sub Sea Developed Field in the North Sea and How 6 Different Companies Contributed

“…In many cases, due to the relatively short production intervals (20ft to 200ft), comparatively uniform permeability and relatively even pressures within layers, achieving an even distribution of the scale squeeze treatment chemicals along the production interval is not problematic. The use of squeeze design software such as SQUEEZE 28 has become the most common way to calculate the treatment volumes required for such treatments and in more complex wells such as Wells A02 and A04 the integration of the SQUEEZE code with Eclipse simulation data to provide better information on fluid placement has proved very effective 12,26,29,30 .…”

Acid/Scale Inhibitor Stimulation Treatment for High-Temperature CHFP Subsea Wells: Fluid Qualification and Formation Damage Assessment

“…While the frac treatment in this application may certainly alleviate the formation damage associated with small amounts of particle plugging, wettability changes remain a significant concern for low permeability, watersensitive, or low water cut oil wells; large amounts of water pumped during the frac treatment will only exacerbate the wettability change / water block problem. Unfavorable wetting alteration and formation damage associated with chemical reactions between scale inhibitors and formation fluids and rock have been recognized, and a number of alternatives have been proposed to minimize the damage (Jordan et al 1998 and2006;Graham et al 1999;Scott et al, 2000;and Guan et al 2003). Strategies include the use of oil soluble scale inhibitors, aqueous inhibitors in conjunction with relative permeability modifying chemicals, and micro-encapsulated scale inhibitors.…”

“…In deepwater developments where there is little room for error and where well intervention is sometimes not even possible, it is extremely important that fluid / fluid and fluid / rock compatibility be assessed prior to pumping the stimulation treatment. The purpose of this work is thus twofold: 1) To evaluate the effectiveness of two acid suites to clean-up Zn powder damage typically encountered during perforations with metal shaped charges, and 2) To qualify the incorporation of an acid pentaphosphonate scale inhibitor widely used in subsea wells (Jordan et al, 1998(Jordan et al, , 1999(Jordan et al, , 2000a(Jordan et al, , 2000b(Jordan et al, , and 2003 to the pre-frac acid in frac treatments targeting high temperature (up to 300 o F) deepwater subsea wells. This paper describes in detail the laboratory qualification of the acid suite, and the acid plus scale inhibitor combination treatment.…”

Enhancing Scale Inhibitor Squeeze Retention With Additives

“…However, in order to provide protection to the reservoir formation, near well bore and downhole production tubing a scale inhibitor squeeze treatment is commonly used. Scale squeeze treatments are a well-established method for mitigating the risks to production caused by scale formation and have been successfully used for decades around the world (King et al 1991;Pardue 1991;Jordan et al 1998;Mackay et al 1998;Boreng et al 1994). A scale squeeze treatment involves the injection of scale inhibitor (usually 10-15% in a suitable carrier fluid) into the reservoir formation where the inhibitor adsorbs to the rock (in the case of an adsorption squeeze) and then desorbs into the produced brine at a high enough concentration to maintain scale control when the well is on production.…”