Development of sand agglomeration formulation for oil and gas well applications to reduce the production of fine particulates
Creators: name: Lee, Rui Yan
Publisher: name: Imperial College London
Year: 2019

description: Sand production is an age-old problem faced by the oil and gas industry which can have severe cost implications if not controlled properly. Approximately 70% of the world’s remaining hydrocarbons are located in sand-prone reservoirs and current approaches to handle sand production are still facing many challenges. The aim of this work was to explore the use of various types of polymers including organic, inorganic and bio polymers in agglomerating formation sand and clays to improve the effectiveness of standalone sand screens. Polymer bridging interactions, charge neutralization and bare patch attraction were the three main agglomeration mechanisms being studied due to their capability of forming aggregates with superior shear resistivity and size. Preliminary studies employing standard zeta potential measurement, laser particle size analysis (LPSA) and scanning electron microscopy (SEM) techniques were found to be of limited use for detailed agglomeration studies. Zeta potential was unsuitable due to Joule heating as a result of the high salinity conditions while the agglomerates encountered very high shear rates which broke them up prematurely during the LPSA studies. SEM had a high degree of error due to capillary forces causing agglomerates to come together, producing larger particle sizes during the drying process. Therefore, a specialized shear test rig was designed, built, and calibrated to undertake agglomeration studies. The Focused Beam Reflectance Measurement (FBRM) and the Particle Vision and Measurement (PVM) probe measurement techniques were employed providing qualitative and quantitative data to monitor the agglomeration process in-situ and in real time. Single, Dual and Multi-polymer agglomeration systems were compared in terms of their agglomeration capabilities based on the mean size changes, fines removal efficiency and agglomerate resistance to shearing effects. Organic polymers studied include polyacrylamides, polyDADMAC and amphoteric polyacrylamides. Inorganic polymers include polyferric sulfate (PFS) and polyaluminium chloride (PAC) while bio-polymers studied include high and low molecular weight chitosan. Polyacrylamides were found to be the best for agglomerating sand, producing superior agglomerate sizes and fines removal compared to the other polymers, in particular for polyacrylamides with very high molecular weights and low-medium charge densities. Polymer chain bridging interactions were responsible for producing stronger and more stable agglomerates which could withstand a constant shear for longer periods. Dual and multi-polymer layering systems were able to produce better agglomeration performance than single polymer systems. High charge density polymers with high molecular weights were found to be relatively good sand agglomeration chemicals as well due to the additional electrostatic interactions forming strong agglomerates. Aging tests for the polymer solutions and their agglomeration capabilities over time at elevated temperatures concluded that the chosen polyacrylamides only sustained a very low degree of degradation over the course of 2 months. Robustness testing also showed that the polyacrylamides allowed a high degree of flexibility during implementation where the same concentration can cope with up to 5-fold sand loading. The novelty of this multi-polymer agglomeration system when coupled with sand screens is in the ability to potentially provide a very cost-effective means to solve sand production issues at the source, eliminating the need for costly remedial solutions at the topside and resin-based sand consolidation methods which impair reservoir permeability. These methods are currently being investigated by PETRONAS for field trials.