Development of Environmentally Friendly Calcium Carbonate Scale Inhibitor for HTHP Squeeze Application in the Oil and Gas Field Water Treatment

The formation of calcium carbonate mineral scale is a persistent and expensive problem in oil and gas production, especially in the high temperature and high pressure (HTHP) wells. Scaling of metallic or insulating walls in contact with hard water may cause unscheduled equipment shutdown and loss of production. The aim of this paper is to develop environmentally friendly calcium carbonate scale inhibitors for HTHP squeeze application in the oil and gas field water treatment.

Typical commercial scale inhibitors, including several phosphonate based squeeze scale inhibitors, and patented environmentally friendly polyacrylic copolymers have been tested based on thermal stability test, formation water compatibility test, dynamic scale loop test and coreflood test.

In this paper, an environmentally friendly calcium carbonate scale inhibitor has been developed to inhibit calcium carbonate scale deposition effectively under HTHP conditions. The characteristics of this product are as following:

•   Thermally stable at high temperature after 7 days.
•   Excellent inhibition performance on CaCO₃ deposition under high temperature.
•   Environmentally friendly and classified as yellow Y1 in Norway.
•   Long squeeze life and no formation damage based on coreflood test.
•   Easy residual analysis by ICP and HPLC to field application concentrations.

This paper will give a comprehensive study of developing environmentally friendly calcium carbonate scale inhibitors for squeeze application for HTHP wells in the oil and gas fields, which includes thermal stability, dynamic scale loop performance, adsorption and desorption performance, compatibility, residual analysis and environmental regulation.

Key words:  calcium carbonate, inhibitor, scale, HTHP