Reservoir Simulation, Ion Reactions and Near-Well Bore Modelling to Aid Scale Management in a Subsea Gulf of Mexico Field

Abstract

This paper presents the findings of a study into the impact of reservoir flow behaviour on both the scaling risk at production wells, and the options for managing this scaling risk, for a deepwater sandstone reservoir in the Gulf of Mexico. One significant feature in this field is that flow takes place through isolated formation layers, and choices made regarding the seawater injection wells have a great impact, not only on the BaSO4 scaling tendency, but also on the placement of scale inhibitor squeeze treatments in the producers. In addition to seawater injection, oil production is supported by the aquifer. The first stage of this study involved identifying the split between connate, aquifer and sea water in the produced brine. This provided data that could be used to calculate the evolution of the scaling risk over the lifecycle of each well. The formation brines contain barium and the injection water is full sulphate seawater, and the relative proportion of each brine, the water production rate, and pressure and temperature conditions all determine the scaling risk. The evaluation of the extent of reactions between the injection water (sulphate) and formation water (barium) from injection to production well can result in a significant reduction in the available barium within the produced water, and hence the scale risk and scale inhibitor concentration required to prevent scale deposition. In this study, as the injection wells were completed with inflow control devices (ICD's) it gave the opportunity to manage the injection split via these ICD's, not only to improve sweep efficiency, but also to balance reservoir pressures and make squeeze treatments more efficient. The study will present the squeeze treatment volumes and estimated treatment lifetimes possible for two scenarios for the water injection application to this deepwater field. The implications of this type of study will be highlighted in terms of the options that this data allows an operator to consider prior to commissioning water injection in these challenging environments.

Selection of Scale Control Strategy on a Sub Sea Developed Field in the North Sea and How 6 Different Companies Contributed

“…This is the first placement option that requires to be assessed before core complex and costly intervention/placement options are assessed. This approach of using reservoir simulation data from Eclipse to better understand fluid ingress and placement as a function of pump rate has been published in the past by the co-authors 12,26,27 and is now viewed as industry best practice in new field developments. In Figures 22 and 23 the location of water production 6 hours, 1 week and 1 year after the bullheaded treatment is presented as green lines for the wells A02 and A04 respectively.…”

“…The squeeze life of any treatment should be determined as the volume of produced water at surface when the first layer reaches MIC not when the concentration at surface reaches MIC as some layer could be well below MIC in heterogeneous wells 26,27 . In the case of well A02 the surface concentration is 10ppm while at least one layer is at the MIC concentration of 2.5ppm.…”

Comparison of Streamline Reservoir Simulation of Brine Flow, Mixing and Barium Sulphate Induced Formation Damage with Observed Produced Water Chemical Data to Aid Scale Management

“…Huseby et al, (2005) improved the reservoir simulation model through making use of geochemical data, and a better match with regard to produced SO 4 2concentration was provided based on tuning the length of a fault. This process was also studied for the Janice field, and produced water chemistry was added as an extra constraint in the history matching process and two kinds of uncertainties on geology and water allocation between injectors were assessed based on the comparison of calculating seawater fraction from simulation model and observed produced water composition (Vazquez et al, 2014). However, geochemical data was only regarded as natural non-reacting ions and the possible geochemical reactions involving them were not considered in these publications, because they normally used a conventional reservoir simulator, such as ECLIPSE, that does not have a chemical reaction model, and so only the flow transport and brine mixing were calculated.…”

“…However, geochemical data was only regarded as natural non-reacting ions and the possible geochemical reactions involving them were not considered in these publications, because they normally used a conventional reservoir simulator, such as ECLIPSE, that does not have a chemical reaction model, and so only the flow transport and brine mixing were calculated. Some applications were demonstrated by Delshad et al, (2003) using UTCHEM, a three-dimensional reservoir simulator, for studying the brine mixing and transport of barium and sulphate ions and barium sulphate scale precipitation taking place within the reservoir and Paulo et al (2001) and Mackay (2003Mackay ( , 2014 applied the flow and reaction simulator to model barite precipitation. However, unfortunately, there were no observed produced water chemical data presented to compare with simulation results in these modelling studies.…”