Pyrite Scale Removal Using Green Formulations for Oil and Gas Applications: Reaction Kinetics

Abstract

Pyrite is one of the toughest iron sulfide scales to remove, which causes major problems in oil and gas production by damaging production equipment. The use of inorganic acid in iron sulfide scale removal particularly pyrite is ineffective and produces toxic gases such as hydrogen sulfide. In this work, H2-S free formulation composed of diethylenetriamine pentaacetic acid (DTPA) combined with potassium or cesium carbonate as the converter is used. The reaction kinetics of pyrite dissolution using a specially designed rotating disk apparatus is investigated. Different characterization techniques such as SEM–EDX, XRD, and XPS were used for the characterization of the pyrite surface before and after chemical treatment. The effects of temperature, rotational disk speed, and converter type on the kinetics are studied. At 130 and 150 °C, the reaction rate increased linearly with the disk rotational speed representing mass-transfer-limited reaction, and the activation energy was 9.94 kJ mol–1. The DTPA diffusion coefficients for the new formulation at 130 and 150 °C were 1.023 × 10–9 and 1.177 × 10–9 cm2 s–1, respectively. The replacement of potassium carbonate by cesium carbonate did not produce a significant effect on the reaction kinetics. Coreflooding tests were carried out using the new formulation of DTPA with K2CO3 to simulate the real dissolution of the scale in pipes, and a solubility of 140 ppm h–1 has been attained. The estimation of the pyrite dissolution rate by DTPA is expected to support engineering design in iron sulfide removal from oil and gas wells.

Electrochemical removal of pyrite scale using green formulations

“…The rate of buildup, k, as well as the other model parameters are given in Table 2 ; the results indicate that the combined formulation of DTPA 10 wt.% with K 2 CO 3 9 wt.% had the highest value. This implied that the rate of buildup is very fast with this formulation corroborating what was observed from our previous works 8 , 27 . It is observed that both the second and third highest buildup rates are also DTPA formulations that is DTPA5K 10 wt.% and DTPA-5Na 10 wt.%, respectively.…”

“…Different green formulations were evaluated to study their potential use as an electrolyte for more efficient pyrite dissolution. These electrolytes were composed from the components of green formulations were used in our previous works for dissolving pyrite scale 8 , 27 . Chelating agents and/or salts were the main components of these formulations.…”

“…The pyrite rock has measured porosity of 0.05%. Chemical analysis for these samples, published elsewhere 27 , shows that it contains more than 99% pyrite with some impurities of Si, Na, Ca, Mg and Al. The working electrode of pyrite was prepared by drilling core samples of 1-in diameter and 0.5-inch thickness disks as shown in Fig.…”

“…The green formulations that are recently reported as an effective dissolver for pyrite were used as the electrolyte in this study 8 , 27 . The chemical dissolution results obtained from our previous work was compared with the electrochemical dissolution data obtained here.…”

Removal of barite from zircon using an aqueous solution of diethylenetriaminepentaacetic acid and potassium carbonate

“…Boiling the pyrite and zircon mixture in nitric acid is a pyrite removal technique used in many laboratories. An aqueous solution of DTPA and potassium carbonate also dissolves pyrite (Ahmed et al, 2019). The DTPA plus potassium carbonate technique described here thus offers the possibility of one-step removal of both barite and pyrite.…”