Predicting Carbonate Scale in Oil Producers From High-Temperature Reservoirs

Abstract

Summary Calcium carbonate (CaCO3) scale is a common problem in the oil industry, leading to reduced well performance and obstruction of the safety valves. Recent field experiences indicate that scaling may be a problem at lowersaturation ratio (SR) than earlier anticipated. In a high-pressure, high-temperature scale cell, crystal growth in synthetic formation water has been studied. Induction times and growth rates have been determined by use of a microscope cell. The results have been interpreted by use of nucleation theory. The findings indicate that wells may be safely operated at SR below 2.5 at85°C. At higher temperature, crystal growth is less dependent on SR and the temperature dominates the system. Care should therefore be taken when operating wells at temperatures greater than 100°C. Introduction Precipitation and deposition of CaCO3 is a common problem in the oil industry. The scaling problems occur during pressure decrease of the produced formation water. The consequence may be reduced performance of the well and in some cases influence on the operation of downhole safety valves(DHSVs).The carbonates precipitate from the produced water as release ofCO2 gas gives increased pH and supersaturation of CaCO3 . The kinetics of the reaction is a function of temperature (i.e., slow kinetics at low temperature). The rule of thumb for prediction of CaCO3 scaling problems has until lately been based upon the work by Oddo and Tomson. Their conclusion from field experiences in the Hitchcock field in Texas, and Farida offshore Indonesia, was that produced water from vertical wells may be supersaturated up to saturation ratio SR=2.51 before any scaling problems occur. The bottomhole temperature was moderate (88 to 104 °C). In some relatively recent field developments, the design of the completion and the need for chemical placement in new wells(e.g., scale inhibitor injection lines) have been partly based on these findings.

Progress on the relationship between miR-125 family and tumorigenesis

“…This involves careful production of the well to avoid large pressure drops, or by choking back wells that produce water which may lead to mixing of incompatible waters (Kelland, 2009;Westgarth, 2013;Ramstad et al 2005). …”

“…Hydrochloric acid (HCl) is the cheapest and easiest acid to use, but the disadvantage is that the acid is very corrosive. This means that a corrosion inhibitor often must be added to the acid solution when being used (Kelland, 2009;Ramstad et al 2005). Most of the reaction products of HCl and carbonates are water soluble and are easily removed (eqn.…”

“…In contrast, barium sulfate is more difficult to handle, being very hard (Al Salami and Monem, 2010;Kelland, 2009;Ramstad et al 2005 …”

The Johan Sverdrup Field – Origin of Sulphate-Rich Formation Water and Impact on Scale Management Strategy

“…The risk of CaCO 3 scale formation in the produced water will increase by high pressure drops (e.g. high drawdown) and high reservoir temperature (Ͼ100°C) (Ramstad et al 2005). Sulphate scale (BaSO 4 , SrSO 4 ) may form due to breakthrough of injected seawater or by mixing of incompatible produced waters.…”

Avaliação Da Incrustação Na Bomba De Fundo Em Poços Produtores De Petróleo E Gás: Estudo De Caso

“…Assim, no poço produtor, a pressão e temperatura diminuem ao longo da coluna até a superfície, mudando as condições termodinâmicas de precipitação nos componentes da coluna (RAMTAD, 2005). Desta forma as incrustações (ou scale) podem ser definidas como compostos químicos de natureza inorgânica que se encontram inicialmente solúveis em soluções salinas, as quais, quando submetidas a mudanças de pressão, temperatura e concentração mudam suas condições de solubilidade (DEMADIS, 2007).…”