Salima Baraka-Lokmane

Scale inhibitor core floods in carbonate cores: chemical interactions and modelling

In previous work (SPE 87447), the effect of pH on phosphonate/carbonate interaction was studied by performing variable pH core floods in short outcrop carbonate cores. Effluent concentrations of scale inhibitor (DETPMP), lithium tracer, calcium and magnesium were measured, as were the corresponding pH profiles. Such detailed sets of measurements are required to interpret the inhibitor/carbonate interaction mechanisms. This previous study showed that carbonate dissolution was evident in all core floods and on how this depended on pH. It also indicated where simple adsorption isotherms could describe this accurately and where this was not the case. Recently, we have performed additional core floods using carbonate core from a second block of this outcrop chalk using DETPMP scale inhibitor slugs at various concentrations and pH values. These results significantly extend previous work and are presented under the following two headings: Scale inhibitor/carbonate/pH interactions in short cores + modelling: Simple flooding cycles are described on the propagation of (Li traced) slugs of pH 6, 4, and 2 (no scale inhibitor) travelling through the carbonate core in order to study the behaviour of calcium, magnesium and effluent pH for various injected brine pH conditions. These results have been modelled and explained using the MultiScale software. “Contained” scale inhibitor floods in long (12”) carbonate cores: Contrasting floods using long (12”) carbonate cores have been performed where <1 PV of DETPMP is injected at the inlet and then back produced. In these floods, the core is never fully saturated and these floods are referred to as “contained” core floods [1]. Very extensive data on SI, cation (Ca, Mg and Li) and pH effluents are collected. These observations lead us to a number of conclusions on the factors that must be included in a full carbonate model. In particular, our experimental results – along with some simple modeling – greatly clarify the role of both calcium and magnesium in the mechanism SI retention in carbonate systems.

Can Green Scale Inhibitors Replace Phosphonate Scale Inhibitors?: Carbonate Coreflooding Experiments

Abstract The oil industry is currently facing severe restrictions concerning the discharge of oilfield chemicals into the environment. The purpose of this study is to test the possibility of replacing an organic phosphonate scale inhibitor (DETPMP) by a more environmentally friendly “green” species: carboxymethyl inulin (CMI). Although, promising these results are nevertheless far inferior to the performance exhibited by the DETPMP coreflood. Squeeze lifetimes of the green scale inhibitor can be improved by increasing scale inhibitor adsorption either by reducing the pH of the injected solution or by changing the chemistry of either injection or postflush brines.

Evaluation of Anti-fouling Surfaces for Prevention of Mineral Scaling in Sub-surface Safety Valves

Mineral scale formation and deposition in down-hole completion equipment such as subsurface safety valves can cause dramatic and unacceptable safety risks and associated production losses and operational costs. Current scale removal strategies involve both mechanical and chemical technologies, each of them having their own advantages depending on the type of mineral scale and its location. However, these techniques are often costly and of limited efficiency. The current study assesses the ability of a range of chemically and morphologically modified coatings to prevent/reduce mineral scale surface fouling. Building-up on previous work done under static conditions, this paper presents results from scaling tests under laminar and turbulent dynamic conditions using a rotating cylinder electrode under in a complex (mixed) scaling environment (supersaturated w.r.t. calcium carbonate, barium sulfate, strontium sulfate, barium carbonate and strontium carbonate). The study shows that if properly selected, surface treatments represent a promising approach to reduce scale deposition on downhole equipment surfaces that are critical to maintain equipment functionality and thereby well safety barrier integrity. By analyzing the scaling behaviors observed within the set of surfaces tested, suggestions of the controlling factors in anti-fouling on these systems are presented and discussed.

Comparison of characteristic of anti-scaling coating for subsurface safety valve for use in oil and gas industry

A subsurface safety valve is used to shut in a well automatically, if the wellhead equipment or other surface production equipment fails. It is almost always installed as a vital component on the completion. In many industrial systems, scale formation causes significant problems, not when it precipitates in bulk solution but when it deposits on the surface. Surface scaling is a complex phenomenon where several processes such as heterogeneous crystallization or particle adhesion are inextricably linked and occur simultaneously. The sub-surface safety valve can accumulate carbonate, sulphate and sulphide scale. Even a thin layer of scale can impede the smooth operation of the valve and pose serious regulatory and safety risks. In this study twenty coatings from seven different natures have been tested. These coatings are Fluoropolymers, Composite (fluotopolymer matrix), Sol-gel nano-coating, Textured hydrophobic paint, Diamond Like Carbon (DLC), Polished Inconel and Nitro carburated Inconel. Whilst the anti-scaling capability of the coating is the key functional element, it is extremely important that the coating presents other important parameters such as hydrophobicity property, surface roughness, coating thickness and hardness, resistance to erosion, corrosion and temperature as well as coating adhesion. In this paper the controlling factors of anti-scaling coatings are discussed. Promising coatings with anti-scaling properties have been identified.

Correlation Between Microstructure and Flow Behavior in Porous Sandstones

Abstract The correlation between permeability and petrographical parameters in cored samples can be used by extrapolations to predict permeability in uncored intervals. The core analysis described here is concerned with the study of fluid-rock interactions in rock samples from three sandstone reservoirs, in particular the effect of petrographical parameters on flow behavior. A positive correlation between liquid permeability and the volume fraction of silica is clearly demonstrated. Liquid permeability was correlated using multivariate regressions to one to five petrographical parameters, the results of which have useful application in the estimation of reservoir permeability where samples are not available for experimental testing.