Restoring Well Productivity Through a Fit-for-Purpose Sludge Cleanout Job

Sludge formation could significantly impair well productivity if deposited in the wellbore or surface flow lines. In a field where sludge formation is not common, an oil production well showed a sudden deterioration in well productivity. Thorough investigation of abnormal well performance, from surface and sub-surface perspective, indicated that the deposition of a thick layer of a tight emulsion across the surface choke has resulted in ceasing the oil flow to the gas oil separation plant. Extensive lab analysis indicated that the obstruction material was a sludge deposition promoted by the presence of asphaltene, high amount of iron and low pH brine. It is noteworthy to mention that the analytical results of lab prepared emulsion samples elucidate the rule of low pH aqueous solution, asphaltene and iron ions in inducing tight emulsion formation which helps to understand the root causes of sludge deposition. To come up with a cost-effective remedial treatment considering health, safety and environment (HSE), different emulsion breaking formulations, including different de-emulsifiers and anti-sludge agents, were examined in this study. An effective diesel-based formulation including proper de-emulsifier and anti-sludging agent was used during the execution of the field job. The design of the field job took into consideration a minimal footprint to the environment through the flowback of the well to the neighboring gas oil separation plant. This paper summarizes the joint efforts by production engineers and lab scientists to systemically tackle such major flow assurance issues which could significantly jeopardize wells productivity. The systemic approach starts with problem detection through well intervention and sample collection. It also includes the lab work which was carried out to identify the type and composition of deposition and evaluate/optimize a proper formulation for sludge deposition removal. The paper discusses in detail the design and execution of a successful field treatment, which has resulted in restoring and maintaining the well potential.

A Numerical Approach to Investigate the Impact of Acid-Asphaltene Sludge Formation on Wormholing during Carbonate Acidizing

Carbonate acidization is the process of creating wormholes by injecting acid to increase reservoir permeability and oil production. Nevertheless, some reservoir oils are problematic with low asphaltene stability, which affects the wormholing process. The interactions between acid, rock, and asphaltene lead to acid-asphaltene sludge formation, which reduces oil productivity and acid injectivity. Neglecting this sludge formation, leads to over predicting the depth of the wormhole penetration. Therefore, a numerical model was developed in this study to provide a better understanding of acid-asphaltene sludge formation effect on wormhole creation and propagation in carbonates. A 1D radial model was developed by coupling fluid flow equations in porous media with asphaltene deposition and acid-asphaltene reactions. Then, the developed model was validated and utilized to investigate the effects of different parameters on wormholing including asphaltene presence, acid injection volume and concentration, formation temperature and porosity, and asphaltene concentration. Results showed that acid injection in carbonates with asphaltenic-oils reduces wormhole penetration from 40% to total pore blockage as opposed to reservoirs without asphaltene deposition. The findings also highlighted that shallow wormhole penetration is more pronounced with high volume of acid injection, high porous formations, less diluted acid, and high concentration of asphaltene. In addition, there is an optimum acid injection volume at which wormhole penetration is high and its infiltration is deep into the formation. This is the first work to discuss modeling of acid-asphaltene sludge formation and subsequent wormhole development in carbonates, which is particularly important for problematic crude oils.

Removal of heavy metal ions from wastewater: a comprehensive and critical review

Removal of heavy metal ions from wastewater is of prime importance for a clean environment and human health. Different reported methods were devoted to heavy metal ions removal from various wastewater sources. These methods could be classified into adsorption-, membrane-, chemical-, electric-, and photocatalytic-based treatments. This paper comprehensively and critically reviews and discusses these methods in terms of used agents/adsorbents, removal efficiency, operating conditions, and the pros and cons of each method. Besides, the key findings of the previous studies reported in the literature are summarized. Generally, it is noticed that most of the recent studies have focused on adsorption techniques. The major obstacles of the adsorption methods are the ability to remove different ion types concurrently, high retention time, and cycling stability of adsorbents. Even though the chemical and membrane methods are practical, the large-volume sludge formation and post-treatment requirements are vital issues that need to be solved for chemical techniques. Fouling and scaling inhibition could lead to further improvement in membrane separation. However, pre-treatment and periodic cleaning of membranes incur additional costs. Electrical-based methods were also reported to be efficient; however, industrial-scale separation is needed in addition to tackling the issue of large-volume sludge formation. Electric- and photocatalytic-based methods are still less mature. More attention should be drawn to using real wastewaters rather than synthetic ones when investigating heavy metals removal. Future research studies should focus on eco-friendly, cost-effective, and sustainable materials and methods.

Sludge Formation Analysis in Hydraulic Oil of Load Haul Dumper 811MK V Machine Running at Elevated Temperatures for Bioenergy Applications

Hydraulic oil degrades expediently during operating at elevated temperatures, and due to oil degradation, malfunction of all hydraulic components starts that hampers the hydraulic functioning of the machine. An inefficient component of the hydraulic system converts useful energy into heat. Overheating starts when the rate of heat energy escaping from the system overcomes the rate of heat dissipation. Viscosity, total acidic number (TAN), rheology, and FTIR analyses were carried out on the oil samples collected chronically, and the reasons for degradation and sludge formation were evaluated; the results showed that thermal cracking resistance capacity of the oil was low due to the imbalance percentage of additives in the base oil. Sludge impaired the system efficiency and prejudicially creates repercussions on power consumption. Sludge can be recycled for biofuel and to avoid imbalance in the ecosystem. The test result is plotted in a 3D view graph using the MATLAB R 2019 software for a better explanation. Variation in the behaviour of the hydraulic fluid with respect to time, temperature, shear stress, and shear rate was studied, and the result is validated with correlation and regression analyses.