A quantitative review of the transition salt concentration for inhibiting bubble coalescence

Some salts have been proven to inhibit bubble coalescence above a certain concentration called the transition concentration. The transition concentration of salts has been investigated and determined by using different techniques. Different mechanisms have also been proposed to explain the stabilizing effect of salts on bubble coalescence. However, as yet there is no consensus on a mechanism which can explain the stabilizing effect of all inhibiting salts. This paper critically reviews the experimental techniques and mechanisms for the coalescence of bubbles in saline solutions. The transition concentrations of NaCl, as the most popularly used salt, determined by using different techniques such as bubble swarm, bubble pairs, and thin liquid film micro-interferometry were analyzed and compared. For a consistent comparison, the concept of TC95 was defined as a salt concentration at which the "percentage coalescence" of bubbles reduces by 95% relative to the highest (100% in pure water) and lowest (in high-salt concentration) levels. The results show a linear relationship between the TC95 of NaCl and the reciprocal of the square root of the bubble radius. This relationship holds despite different experimental techniques, salt purities and bubble approach speeds, and highlights the importance of the bubble size in bubble coalescence. The available theoretical models for inhibiting effect of salts have also been reviewed. The failure of these models in predicting the salt transition concentration commands further theoretical development for a better understanding of bubble coalescence in salt solutions

Novel methodology for predicting the critical salt concentration of bubble coalescence inhibition

Bubble coalescence in some salt solutions can be inhibited if the salt concentration reaches a critical concentration Ccr. There are three models available for Ccr in the literature, but they fail to predict Ccr correctly. The first two models employ the van der Waals attraction power laws to establish Ccr from the discriminant of quadratic or cubic polynomials. To improve the two models, the third model uses the same momentum balance equation of the previous models but different intermolecular force generated by water hydration with exponential decaying. The third prediction for Ccr requires the experimental input for film rupture thickness and is incomplete. We show further in this paper that the third model is incorrect. We propose a novel methodology for determining C cr which resolves the mathematical uncertainties in modeling C cr and can explicitly predict it from any relevant intermolecular forces. The methodology is based on the discovery that Ccr occurs at the local maximum of the balance equation for the capillary pressure, disjoining pressure, and pressure of the Gibbs-Marangoni stress. The novel generic approach is successfully validated using nonlinear equations for complicated disjoining pressure

Prediction of the flowing bottom-hole pressure using advanced data analytics

Flowing bottom-hole pressure (FBHP) is a key metric for optimising coal seam gas well performance and enhancement of production. Downhole pressure gauges are increasingly being used to measure the FBHP. However, they are impractical, expensive, and complex to install and maintain. Consequently, reliable measurement and prediction of the FBHP, required to forecast well production, remains a challenge. This paper aims to predict the flowing bottom-hole pressure in coal seam gas wells by taking advantage of the temporal data and advanced analytics. Data-driven models have been developed to predict the FBHP by leveraging the temporal data gathered at the surface in order to control the performance of the wells. The data used in the study was obtained from five coal seam gas wells containing seven sensor measurements gathered over 15-18 months production period. For the prediction of FBHP, we applied linear regression and neural network-based approaches. Overall, neural networks resulted in the best predictions with the root mean squared error (RMSE) within 198-450 kPa for the five wells

Evaluation of interfacial properties of concentrated KCl solutions by molecular dynamics simulation

Understanding the interfacial properties of concentrated salt solutions is critical for various applications in physical, chemical and biological processes. This study aims to evaluate the interfacial properties of potassium chloride (KCl) solutions with concentrations ranging from 1 to 4M using the molecular dynamics simulation technique. We used two different water models, TIP4P/2005 and SPC/E to calculate the local density and angle distribution, viscosity, interfacial tension and surface potential of the salt solutions. The surface tension values predicted by the TIP4P/2005 model showed an incremental trend in agreement with experimental data. For viscosity, the predictions of TIP4P/2005 are close to the experimental data, while the predictions of SPC/E are in poor agreement with the measured viscosities. Our results show that the selection of water models significantly affects the structure properties of concentrated KCl solutions. Also, the TIP4P/2005 model compares very closely with the measured interfacial properties of salt solutions

Data collation, preparation, and initial analysis

The purpose of this report is to update industry partners, with respect to the 2 primary aims of the project. This project aims to leverage existing data for enhanced production efficiency via estimation of flowing bottom-hole pressure for wells with no downhole pressure gauge and prediction of impending pump failure. This report specifically aims to address the following objectives within six months from the commencement of the project:·\ua0\ua0Reviewing available data, including assessment of current data quality and organisation, and implications for analysis, as well as recommendations of best practices.·\ua0\ua0Investigating the feasibility of applying machine learning to PCP data by testing various machine learning algorithms to predict the flowing bottom-hole pressure and failure modes

Effect of Divalent and Monovalent Salts on Interfacial Dilational Rheology of Sodium Dodecylbenzene Sulfonate Solutions

This study presents the equilibrium surface tension (ST), critical micelle concentration (CMC) and the dilational viscoelasticity of sodium dodecylbenzene sulfonate (SDBS)-adsorbed layers in the presence of NaCl, KCl, LiCl, CaCl2 and MgCl2 at 0.001–0.1 M salt concentration. The ST and surface dilational viscoelasticity were determined using bubble-shape analysis technique. To capture the complete profile of dilational viscoelastic properties of SDBS-adsorbed layers, experiments were conducted within a wide range of SDBS concentrations at a fixed oscillating frequency of 0.01 Hz. Salts were found to lower the ST and induce micellar formation at all concentrations. However, the addition of salts increased dilational viscoelastic modulus only at a certain range of SDBS concentration (below 0.01–0.02 mM SDBS). Above this concentration range, salts decreased dilational viscoelasticity due to the domination of the induced molecular exchange dampening the ST gradient. The dilational viscoelasticity of the salts of interest were in the order CaCl2 > MgCl2 > KCl > NaCl > LiCl. The charge density of ions was found as the corresponding factor for the higher impact of divalent ions compared to monovalent ions, while the impact of monovalent ions was assigned to the degree of matching in water affinities, and thereby the tendency for ion-pairing between SDBS head groups and monovalent ions

Enhancing CSG well production through well bottom-hole pressure control: laboratory work and mathematical modelling

Confidential industry report prepared for Shell, Arrow Energy, Santos and APLNG