Scale deposition in oil and gas wells is a major issue in the oil and gas industry as it reduces hydrocarbon production, restricts well access to production logging tools and, in addition, causes safety issues due to blocking and ineffective operation of chokes and valves. Scale is predominantly controlled with chemical scale inhibitors and the most common methods to control scale deposition are through continuous injection and scale squeeze treatments although some non-chemical methods can be applied.
The performance of continuous injection and scale squeeze treatments is traditionally monitored by the analysis of scaling ion and residual inhibitor concentrations (RSI) in collected produced water samples in conjunction with other parameters such as productivity index (PI) and temperatures and pressures throughout the whole production system. However, these methods are not always sufficient to identify the onset of scale formation and there can be some uncertainty as to whether the produced water is fully protected.
It is therefore desirable to have an alternative to more conventional monitoring methods to assess the actual scaling regime of produced brine samples. This can be achieved by analyzing suspended bulk scale solids using Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis (ESEM/EDX).
ESEM bulk scale analysis can measure particle size, identify morphology and the chemical composition of any bulk scale produced. The method provides accurate statistics of the amount of the different types of scale, which can both be an early warning indicator as well as a key parameter for trending over time together with other relevant parameters such as scaling ions, RSI and PI. In addition, machine learning has been applied to images of representative scale particles to classify them as either transported (pre-formed)/modified by the selected scale control process or actively growing.
The intelligent investigation of particle morphology provides a further understanding of the mechanisms of inhibition and enables a prediction of the % efficiency of scale inhibition. Therefore, ESEM bulk scale analysis offers a more direct approach to monitoring the scaling regime of produced brines and can identify if scale prevention is needed and indeed, whether any applied chemical or non-chemical treatments are effective. Specific field examples are provided in this paper where the technique was used to reduce chemical costs and improve the performance of scale squeeze treatments in terms of placement and longevity.
This paper discusses how ESEM bulk scale analysis can improve scale management in a variety of production scenarios and demonstrates how the technique can provide a more direct monitoring tool enabling meaningful trend observations and better reactions and decisions to be made to reduce environmental impact factors and contribute towards net zero.
