Understanding the Co-deposition of Calcium Sulphate and Barium Sulphate and Developing Environmental Acceptable Scale Inhibitors Applied in HTHP Wells

Abstract

Calcium sulphate and barium sulphate are two major scales experienced in the oil and gas fields, especially when sea water breakthrough in the waterflood supported HTHP wells. Normally, studies have been focused on a single scale component. Seldom studies have focused on the co-deposition of calcium sulphate and barium sulphate. The importance of interference between calcium sulphate and barium sulphate deposition in the field, especially for the HTHP wells, has been ignored.In this paper, the interference between calcium sulphate and barium sulphate deposition has been studied based on a field case in the North Sea. The mechanisms of co-deposition have been addressed using both scale prediction and laboratory tests. Environmentally acceptable scale inhibitors have also been developed.The scaling tendency and mass deposition of calcium sulphate and barium sulphate have been predicted with sea water breakthrough at different levels. The difference between calcium sulphate and barium sulphate, and the consequences of both types of scale deposition are discussed.Dynamic scale loop tests have been carried out. It demonstrated that a small amount of barium sulphate deposit substantially accelerates the co-deposition of barium sulphate and calcium sulphate. Linked to the scale prediction, the mechanism of co-deposition of calcium sulphate and barium sulphate has been addressed.Several scale inhibitors, including phosphonate and polymer based inhibitors, along with an amine based polymer have been tested under the worst case scaling condition. Environmentally acceptable scale inhibitors have been developed and are suitable for squeeze application. This paper will give a comprehensive study of co-deposition of calcium sulphate and barium sulphate, including scale prediction, laboratory evaluation, mechanism discussion and inhibitor selection. It will contribute to understand calcium sulphate and barium sulphate scale deposition in HTHP wells and find effective inhibitors for field application.

Effect of temperature and calcium ion concentration on permeability reduction due to composite barium and calcium sulfate precipitation in porous media

“…The results of this study showed that the effect of calcium sulfate solubility and the size of deposited scales take over the effect of barium sulfate solubility, so the intensity of permeability reduction in composite scale formation experiments increases. This result is in good agreement with the work of Liu et al (2012) which their experimental research showed that the intensity of composite BaSO 4 eCaSO 4 deposition in coil tube was clearly greater than the intensity of pure BaSO 4 and pure CaSO 4 scale deposition.…”

“…Immense amounts of information about these scales have been documented by Kan and Tomson (2012) of which a summary is presented in Table 1. A few studies (Sudmalis and Sheikholeslami, 2000;Chong and Sheikholeslami, 2001;Hennessy and Graham, 2002;Jones et al, 2004;Tung et al, 2004;Sheikholeslami, 2011;Liu et al, 2012) have been conducted to investigate composite scale formation. Sudmalis and Sheikholeslami (2000) stated that coprecipitation of CaCO 3 and CaSO 4 in static batch tests affects the thermodynamics and kinetics of single CaSO 4 and CaCO 3 as well as scale structure.…”

“…Their results showed that the barium sulfate solubility increases in the presence of calcium ions due to effect of ionic strength and based on ion-poising. Liu et al (2012) performed dynamic scale loop tests to examine the intensity of BaSO 4 and CaSO 4 co-deposition. They observed that co-deposition of BaSO 4 and CaSO 4 blocked the coil tube (1 mm in diameter) in a very short time compared to single BaSO 4 or CaSO 4 scales.…”

Progress on the relationship between miR-125 family and tumorigenesis

“…The precipitation of these solids occurs as a result of changes in the ionic composition, pH, pressure and temperature of the brine. When water flooding method is applied for enhance oil recovery, then the problem of scale may occur right from water injection facilities to the producing well, and generally scale can occur during and after injection operation in the injector wellbore, near the injection well bottom hole, in the reservoir between the injector and producer, at the skin of producer well, in the producer wellbore, oil well casing, oil pipelines and other production facilities (Liu et al 2012;Dickson et al 2011). …”

Synthesis and performance of a polymeric scale inhibitor for oilfield application

“…Scale is often defined as the precipitation from aqueous solution with inorganic sediments and scale deposition is a problem commonly existing in different processes in oilfield productions, for instance, water injecting, oil extracting, gathering and transporting, warming treatment, demulsification, crude oil dehydration and desalting, etc., meanwhile, the scale is prone to be appeared on the down hole, oil well casing, oil pipelines and other production equipments (Liu et al 2012;Dickson et al 2011). The scale deposition products in oilfield are mainly consisted of calcium carbonate, calcium sulfate, barium sulfate and strontium sulfate, iron, silicon sediment and other insoluble solids (Senthilmurugan et al 2011;Dickinson et al 2012) and the production of scaling is often due to the changes of thermodynamics conditions or the fluids incompatibility.…”