Minimizing the Barite Scale in Carbonate Formations during the Filter Cake Removal Process

Abstract

The barite scale is one of the most common scales in the oil and gas industry. It can form in the reservoir or precipitate in different production equipment. The formation of such a scale will significantly minimize the capillary diameter of the flow channels and consequently shrink the well productivity. On the other hand, the production of movable barite particles causes severe erosion for the installed equipment. There are several sources of the barite scale such as mixing of incompatible brines and solid invasion of the barite weighted during drilling. In addition, the barite scale could be produced during the interaction of the chelating agent solutions with the reservoir formation during the filter cake removal process (secondary damage). The main focus of this study is to prevent the barite scale inside the carbonate formations during filter cake removal. The capability of a solution consisting of both diethylenetriamine pentaacetic acid (DTPA) and ethylenediamine tetraacetic acid (EDTA) as a novel solution to prevent barite scale formation in carbonate formations after the removal of the barite filter cake was evaluated. A series of laboratory experiments were accomplished to characterize the barite scale and evaluate the performance of the proposed solution. In particular, particle size distribution, scanning electron microscopy, X-ray diffraction, core flooding, NMR spectroscopy, solubility test, and inductively coupled plasma (ICP) spectroscopy tests were conducted for this aim. The experiments were performed using carbonate core samples. The results showed that the proposed solution was able to load 35 000 ppm barium in the presence of calcite ions. The addition of EDTA tended to inhibit the barite deposition and improve the rate of the calcite reaction. NMR results showed that a mixture of DTPA and EDTA (20%) can stimulate the macropores, resulting in an increase in the return permeability by 1.4–1.8 times of the initial value, while the precipitation that occurred in the micropores could be ignored with respect to the overall porosity improvements.

Chelating Agents in the Oilfield

“…It was also shown that combinations of chelating agents such as DTPA/GLDA, DTPA/EDTA, or DTPA/MGDA resulted in lower performance than DTPA alone. This is mainly because barite dissolution is inhibited by the physical presence of other chelating agent molecules [66,67]. It was also noted that barite dissolution with DTPA increases as temperature increased, indicating a thermally activated process [63,68,69].…”

Barite Removal Using Macropa: Simulation and Solubility Investigations

“…An important objective is to increase the barite solubility by exploring different chemical systems under various conditions. Several types of chelating agents were proposed to remove the barite deposition including DTPA, GLDA, EDTA, HEDTA, and NTA. , In addition, mixtures of chelating agents and different types of catalysts were studied to improve the barite solubility. ,, The dissolution of barite in aqueous DTPA was enhanced using potassium carbonate, potassium formate, potassium chloride, potassium nitrate, ammonium chloride, ammonium carbonate, sodium carbonate, calcium chloride, and magnesium chloride. ,, The barite solubility can be increased by adjusting the pH, increasing the pH above 12 showed a considerable improvement in the barite solubility because of the higher binding affinity of carboxylates compared to protonated carboxylic acid groups. , 20 wt % DTPA prepared using potassium base salt and with pH above 11 showed barite solubility of around 67% while adding converting agents such as potassium carbonate or potassium chloride led to increasing the solubility to above 90%. ,, The use of converting agents might lead to other types of formation damage due to the incompatibility between the additional additives and the formation. − …”