Gelled Scale Inhibitor Treatment for Improved Placement in Long Horizontal Wells at Norne and Heidrun Fields

Abstract

Summary The success of a scale inhibitor treatment depends on placement efficiency. The scale inhibitor should be placed so that all water-producing intervals accept a sufficient quantity of the total treatment volume. If significant permeability or pressure variations are present in the interval to be treated, treatment fluid will enter the zones with the higher permeability and lower pressure, leaving little fluid to treat the other zones, which can be the water- producing zones. The challenge is even greater in long, horizontal wells with significant permeability and pressure contrast. To achieve a more uniform fluid coverage, the original flow distribution across intervals often needs to be altered. The methods used to alter this are called "diversion" methods. The purpose is to divert the flow from one portion of the interval to another. In response to this challenge, a joint study with the objective of improving the placement of treatment fluids was initiated by a major operator in the North Sea and two service companies in 2002. The joint work resulted in development of a fully viscosified scale inhibitor system. The system comprises a purified xanthan viscosifying agent, a standard scale inhibitor for downhole scale squeezing, and a breaker to achieve controlled gel breaking down hole. The system has been field tested at Norne field in two long horizontal wells and at Heidrun field in one long deviated well, all with significant permeability variations and crossflow. The operations were successful and the scale treatments have protected the wells from scaling. This paper describes the product qualification process, placement simulation, temperature prediction, gel breaking characteristics, case histories, and post-job evaluation.

Impact of Successive Squeezes on Treatment Lifetime and Well Productivity: Comparative Assessment of Viscosified and Non-Viscosified Treatments

“…Only a single viscosified squeeze has been performed on the Heidrun field (Selle et al, 2008) while on Norne several of the wells have undergone successive viscosified squeezes.…”

“…With regards the squeeze performed on Heidrun, Selle et al (2008) described the pumping operation for the viscosified squeeze. It was observed during pumping that as soon as the front of the viscosified treatment started to enter the formation pressure increased by 50 bar at the same pump rate with corresponding reduction in injection rate.…”

“…Over the past decade, as horizontal completions have become the norm as means for increased hydrocarbon drainage, the limitations of non-viscosified treatments have been exposed. Several papers have been published that cover the downhole scale management challenges associated with horizontal wells and field experiences in the use of viscosified treatments (James et al, 2005;Selle et al, 2008). The first field application of a viscosified treatment was in 2004 on the Shell operated Nelson field in the Central North Sea.…”

Synthesis and Sorption Study of AlOOH Nanoparticle Cross-Linked Polymeric Scale Inhibitors and their Squeeze Performance in Porous Media

“…Viscous fluids with both Newtonian and non-Newtonian properties were investigated experimentally and theoretically in the last decades to better control their placement (Selle, et al 2009;Sorbie, et al 2006;Heath, et al 2008). Simulation of applying shear-thinning inhibitor slug showed dramatic effects on inhibitor placement in a linear heterogeneous system (Sorbie, et al 2006).…”

“…Simulation of applying shear-thinning inhibitor slug showed dramatic effects on inhibitor placement in a linear heterogeneous system (Sorbie, et al 2006). Field tests of squeezing viscosified scale inhibitors have shown successful prevention from scaling (Selle, et al 2009). The viscosity of squeezed species and their retention could be increased by mixing various types of polymers.…”