Evaluate the Usage of Eco-Friendly Bio-Oils as Asphaltene Anti-Sludge Agent in Matrix Acidizing

Abstract

Asphaltene precipitation, flocculation, and deposition are vital problems that may cause serious damage to reservoirs, wells, and production facilities. Asphaltene precipitation may occur during primary depletion or acidizing jobs, as well as after the injection of rich gas or carbon dioxide. The organic deposition removal is considered a costly workover job with the current oil prices. The solvents that are usually used are toluene and xylene, which are considered carcinogenic and toxic chemicals. The use of dispersion to inhibit the organic deposition is essential and can be expensive, as it is required for the life of the well.

This project was aimed to find an alternative bio-oil dispersant that can be used as an eco-friendly and cost effective option. Coconut oil and andiroba oil were tested against chemical asphaltene dispersants to inhibit asphaltene in Kuwaiti crude oil. The effectiveness of the bio-oils was studied under reservoir temperature at 70°C and several concentration of the dispersants were tested to achieve optimum performance.

Acid induced asphaltene sludge is a well-known problem that can result in loss of the well in some cases, after acidizing an oil well. The majority of the development in the industry has been focused on controlling the iron concentration instead of stabilizing the asphaltene while interacting with the acid. The anti-sludge agent used is DBSA or it’s derivate.

A Kuwaiti crude oil was used in this study having an API of 38° and 2% asphaltene content. The crude oil was characterized by a variety of analytical techniques including: total acid and base numbers (TAN, TBN), saturates, aromatics, resins and asphaltene analysis (SARA), density, viscosity and elemental analysis. Indiana limestone and Carbon tan cores were used with average porosity of 16% and permeability ranges (9-30) md. X-ray diffraction (XRD) and scanning electron microscopy was used to analyze the mineral and clay content in the cores. Sludge tests were used to examine the acid and oil compatibility using a aging cell under 500 psi and 70°C. Coreflooding experiments under reservoir condition were done with the selected two acid systems, 15 wt. % HCl and chelating agent (GLDA). CT scans were done on the cores at dry, wet, oil-saturated and after acidizing and then were used to analyze the porosity profile within the core. The produced fluids were also analyzed by pH values of spent acid solutions.

This study provides a novel idea of using bio-oils as anti-sludge agent in matrix acidizing. The use of coconut oil with GLDA in matrix acidizing considered a 100% green stimulation system with high bio-degradability.

This study concluded that the use of dispersant can help reduce the asphaltene sludge and create better acid propagation through the core. The coconut oil gave a comparable performance to chemical dispersant in limestone acidizing with 15 wt. % HCl. Limestone acidizing with GLDA showed the coconut oil outperforming the chemical dispersant by reducing the injected pore volume needed to breakthrough. The results can be employed to design the optimum better acid formulation and create the desired wormhole in limestone formation.