Abstract

CO2 intrusion into the drilling fluid during bauxite drilling can cause hydration swelling and dispersion of clays and lead to massive foaming of them. Additionally, the formation develops micro-nano fractures, which also have a large difference in compressive strength and a high percentage of bound water. Once the foreign fluid invades, it will lead to wellbore destabilization and reservoir damage. Thus, the designed drilling fluid formulation does not contain solid phase particles such as bentonite. And we obtained the optimal proportion of hydrolocker, penetrant, and defoamer by Mixture Designs. Then the shielding plugging theory was introduced, and a temporary plugging gradation consisting of acid-soluble inert particles, deformable nano-sealers, and non-permeable sealers was constructed with the aid of BridgePro software. And other surfactants were optimized indoors to build a low-damage, strong anti-CO2 pollution water-based drilling fluid. It could resist the high temperature of 150℃ and has a remarkable ability to lower surface tension (17.3mN). The rolling recovery, the plugging rate, and permeability recovery value can reach more than 90%, the lubrication coefficient was around 0.125. The constructed drilling fluid completed 9 wells in field application, with an obvious reservoir protection effect and an average increase of more than 20% in single-well daily production compared to the expected daily production. It will be an important reference for future bauxite horizontal well drilling fluids to prevent CO2 contamination and reduce reservoir damage.

Abstract

CO2 emission reduction has become the consensus of various industries in China. CO2 capture, utilization and storage, as an important means for CO2 emission reduction, is one of the necessary paths to achieve carbon neutrality. Combined with the CO2 emission of a chemical industry company in the region of East China, this paper introduces the recovery methods, processes and costs of different CO2 emission sources, and analyzes the CO2 emission reduction path for the company. Results showed that the process complexity and unit cost of CO2 capture decreased with the increase of concentration of CO2 emission sources, the carbon recovery cost per ton of high concentration CO2 emission source is only about 1/3 of that of low concentration CO2 emission source, which has significant economic benefits on the premise of downstream absorption pathway. Therefore, priority should be given to the recovery of high concentration CO2 emission sources. The carbon recovery economy of low concentration CO2 emission sources is poor, so priority should be given to using new energy to reduce their emissions, and coupling new energy technologies in the recovery process to reduce the recovery cost.

Abstract

To clarify the driving mechanisms of carbon capture, utilization, and storage (CCUS), phase behaviors in bulk CO2-oil-brine system is inevitably foundational investigation. In this study, we conducted pressure-volume-temperature tests under single-variable control in laboratory with in-situ crude oil and synthetic brine samples. First, constant composition expansion tests were designed to examine saturation pressure between CO2 and oil phases with varied CO2 mole concentration and temperature, respectively. Meanwhile, as a major mechanism for carbon storage, CO2 solubility in brine and oil was then measured with changing pressures at a specific reservoir temperature. Growth of the saturation pressure was constantly detected with increasing CO2 mole concentration and temperature, respectively. With sufficient CO2 guaranteed during the tests, we found that CO2 solubility in tested liquids was strengthened by the pressure increase as expected. Moreover, within the same pressure range, incremental CO2 solubility in oil was about ten times larger than that in the brine, which indicated potentially underestimated CO2 storage capacity in depleted oil reservoirs.

Abstract

Based on the cubic equation of state, the effect of impurities such as nitrogen, methane, hydrogen and oxygen on the characteristics of phase behavior of carbon dioxide (CO2) was discussed in this study. A prediction model of the phase characteristics of CO2 system containing impurities was established by correlating phase equilibrium and critical state prediction. Additionally, a mathematical model for the calculation of physical properties of the multi-component system was established. The changing rules of the physical properties including density, viscosity, Joule-Thomson coefficient, and specific heat capacity at constant pressure were analyzed. Based on the constructed prediction model, the analysis of phase properties and physical properties of impurity-containing CO2 streams under various transport conditions was carried out. The comparison of the prediction results with the experimental results shows that the prediction accuracy was improved under certain conditions, which provides a certain theoretical basis for the analysis of pipeline transmission chain in the CCUS engineering practice.