Novel Scale Squeeze Technology and Treatment Designs for Improving Scale Inhibitor Retention and Treatment Lifetimes - Use of Ionic Polymers in the Overflush

Abstract

A common method to prevent scale forming in oil production wells is to inject scale inhibitor into the formation in so called squeeze treatments. Conventional scale inhibitor treatments with a brine pre-flush, main scale inhibitor pill and brine over flush stages are often not considered to be economically efficient as a large proportion of the scale inhibitor introduced into the squeeze treatment is returned almost immediately and therefore does not serve to provide long term scale protection. Various techniques have been used successfully to increase the proportion of scale inhibitor retention in the well during squeeze treatments. For example, it has been reported previously in many papers where poly amino acids and poly quaternary amines have been injected into a well as part of the pre flush process and have significantly improved scale inhibitor retention and scale squeeze lifetimes. It has now been found that scale inhibitor treatment lifetimes can be improved by incorporating an ionic polymer such as a poly amino acid or poly quaternary amine in the over flush stage of the squeeze treatment. Indeed this method has been found to further extend the treatment lifetimes when combined with the same additives in the pre-flush stage of the scale squeeze treatment. The new scale squeeze design technology can be considered very flexible as it can be applied with most scale inhibitor chemistries including both phosphonates and polymers with minimal formation damage potential compared to most precipitation scale squeeze treatments. It should be applicable over a wide temperature range from 30°C to 200°C and, in addition, the treatment strategy also lends itself to both aqueous and non-aqueous deployment and hybrid treatments and could provide extra protection against fines production in water sensitive wells depending upon the ionic polymer deployed. Initial field treatments have demonstrated the potential to extend treatment lifetimes by retaining up to 20 to 50% more useful chemical in the treatment reservoir. This paper will highlight the proposed mechanisms of how the ionic polymer additives can improve squeeze treatment lifetimes as part of the over flush and will present field data for treatments on two wells in an HP/HT field at 165°C that demonstrated improved chemical retention and scale inhibitor returns compared to treatments without the ionic polymer additive in the over flush.

Evaluation of Barium Sulfate Scale Inhibition Using Relative Permeability Modifier Polymers as Adsorption Enhancer for Mature Offshore Well Treatments in Campos Basin, Brazil

“…Test 1 inhibitor release curve presented the expected inhibitor release trend reported in literature. − Test 2, however, presented an atypical curve. Lithology of core sample for test 2 comprises less mineral variety than that of samples from test 1: In particular, no clay mineral was detected in core samples for test 2.…”

The state of the art in scale inhibitor squeeze treatment

“…It was observed that such cations might improve scale inhibitor retention during a squeeze. Therefore, quaternary amine types of chemicals are proposed to be used in both preflush and overflush as a bridging agent for inhibitor retention (Selle et al 2003;Heath et al 2012;Sitz et al 2012). Amine groups are also incorporated into the anionic polymer to improve the anionic inhibitor retention in the formation rock in squeeze treatments (Jordan et al 2011b;Chen et al 2011).…”

Oil Field Mineral Scale Control

“…In another study, Sorbie et al [37] examined the shear-thinning effect on inhibitor placement in a non-Newtonian environment. Heath et al [39] outlined the proposed mechanisms of how the ionic polymer additives as part of the overflush can improve squeeze treatment lifetimes. In a radially heterogeneous system, viscous fluids caused a much larger diversion in the linear model than in the radial case, and the shear thinning did not significantly influence scale inhibitor slug placement.…”