Abstract

Scale formation presents a flow assurance challenge to the oil and gas industry. Scale inhibitor squeeze treatments are the most common method used to prevent scale deposition in subsurface applications. Software tools exist which are routinely used to assist with the challenges posed by scale. An important step in using predictive simulation models is validation. Validation requires the collection of field or laboratory data for comparison with the model predictions. The cost and value of various data required for designing scale inhibitor squeeze treatments with SQUEEZE VI has been assessed.

The first stage of designing a scale inhibitor squeeze treatment is chemical selection. Corefloods are used to derive an inhibitor-rock interaction function called an isotherm. The possible consequence of terminating a coreflood too early has been demonstrated. An opportunity for reducing the man-hours required to derive an isotherm has been identified.

The water production and injection profile in a well is valuable information which, when incorporated into a squeeze treatment model, improves the accuracy of the model's prediction. Possible methods for obtaining this data have been reviewed. The consequences of modelling a squeeze treatment with the wrong flow profile have been demonstrated.

After executing a squeeze treatment brine samples are collected and scale inhibitor concentrations are measured. This data is used to determine when the treatment should be repeated and to history match the squeeze treatment model. The cost per barrel of treated fluid may be reduced by collecting samples less frequently. The impact and risk of reducing the sampling frequency on the ability to predict a treatment's lifetime is demonstrated. Lastly, the possible outcomes of reducing the sampling frequency on the ability to effectively history match a model are demonstrated.

Introduction

Scale formation presents a flow assurance challenge to the oil and gas industry. For example, BP estimated that 18 % of their well downtime during the period 1999–2003 was attributable to scale (Vazquez 2007). Scale is defined as a hard crystalline deposit resulting from the precipitation of mineral compounds present in water. The crystalline deposits are formed due to the minerals adhering themselves to solid surfaces. These solid surfaces may be in the reservoir, the production tubing, or the surface facilities. As such, the problems caused by scale deposits are many: formation damage, blockages in perforations or gravel pack, restrict/block flow lines, safety valve and choke failure, pump wear, and corrosion underneath deposits. Further complications are encountered due to some scales being radioactive. Examples of scale deposition are shown in Figs 1 and 2.

This content is only available via PDF.
You can access this article if you purchase or spend a download.