Inspirations from Field-Reservoir CO2 Flooding with Different Miscible Degrees under Cross-Scale Oil Reservoir Conditions.

In recent years, CO2 flooding has become one of the main enhanced oil recovery (EOR) methods, especially for tight formations in different oilfields around the world. Most of the CO2 flooding projects carried out in the world are based on miscible flooding, however, this technique is less effective in China because of the depth of the reservoirs and the heavy components of the crude oil. Near-miscible flooding and immiscible flooding have also been gradually applied to China's domestic oil fields, and have achieved certain oil increase effects, but there are still some challenges such as gas channeling, corrosion, and solid phase deposition in the process of CO2 flooding. In this paper, through a detailed review of recent domestic and foreign cases of enhanced oil recovery, the effects of development methods of low permeability and ultralow permeability reservoirs under different miscible degrees are analyzed, and the solutions to some of the existing problems in field tests and experience are systematically summarized. According to the results of field tests, both miscible flooding and near-miscible flooding have similar effects and can achieve better recovery increment, with a long effect period and slow gas breakthrough speed. In addition, the problems of gas channeling, corrosion, and solid phase deposition occurring in the process of CO2 flooding are analyzed, and solutions such as a change in injection methods and coatings are put forward, which effectively promote the development of CO2 flooding technology. Those suggestions are of great significance for improving the oil recovery rate of unconventional oil reservoirs, ensuring the national energy supply, and low-carbon emissions reduction in China.

Predictors of good outcomes and mortality after thrombectomy for basilar artery occlusion within 12 hours of onset.

BACKGROUND: Patients with acute basilar artery occlusion (ABAO) who undergo combined standard medical treatment (SMT) and endovascular thrombectomy (EVT) may still have unsatisfactory outcomes. This study was conducted to identify the factors that may impact their outcomes. METHODS: We retrospectively reviewed the data of all patients with ABAO combined with SMT and EVT in the endovascular treatment for acute basilar artery occlusion (ATTENTION) trial. A good outcome is defined as a modified Rankin Scale (mRS) score of 0-3, a poor outcome as mRS score of 4-6, and mortality as death at 90-day follow-up. The study analyzed various factors influencing the patients' good outcomes and mortality. RESULTS: The study included 221 patients (148 men and 73 women). Among these patients, 45.7% achieved an mRS score of 0-3, while the overall mortality rate was 37.1% (82/221). A good outcome was significantly associated with younger age (adjusted OR 0.96; 95% CI 0.93 to 0.99; P=0.019), a baseline posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) of 8-10 (adjusted OR 2.34; 95% CI 1.07 to 5.12; P=0.034), and post-procedure pc-ASPECTS of 8-10 (adjusted OR 1.40; 95% CI 1.07 to 1.84; P=0.013). Additionally, time from puncture to reperfusion (adjusted OR 2.02; 95% CI 1.2 to 3.41; P=0.008) and intracranial hemorrhage (adjusted OR 3.59; 95% CI 1.09 to 11.8; P=0.035) were associated with 90-day mortality. CONCLUSIONS: Younger age, baseline pc-ASPECTS of 8-10, and higher post-procedure pc-ASPECTS could effectively predict good outcomes for patients with ABAO undergoing EVT. Additionally, a prolonged time from puncture to reperfusion and intracranial hemorrhage can independently predict mortality. TRIAL REGISTRATION NUMBER: NCT04751708.

The Role of Hyperdense Basilar Artery Sign in Predicting Outcome of Acute Basilar Artery Occlusion within Twelve Hours of Onset.

BACKGROUND: The correlation between hyperdense basilar artery sign (HDBAS) and outcome after acute basilar artery occlusion (ABAO) is debated. Our objective was to determine the usefulness of HDBAS in predicting the outcomes of patients with ABAO after endovascular treatment (EVT), intravenous thrombolysis (IVT), and best medical treatment (BMT). METHODS: The study participants were selected from the ATTENTION trial. The primary outcome of the study was a 90-day modified Rankin Scale (mRS) score, and the secondary outcome was the recanalization rate, any intracranial hemorrhage, and 90-day mortality. RESULTS: The study comprised 276 participants, with cohorts for EVT (n = 188), IVT (n = 82), and BMT (n = 88). In the EVT cohort, HDBAS was not associated with 90-day mRS score (adjusted odds ratio [OR], 0.87; 95% confidence interval [CI], 0.51-1.48; P = 0.6029), the recanalization after 24 hours of onset (adjusted OR, 0.76; 95% CI, 0.30-3.61; P = 0.9422), and 90-day mortality (adjusted OR, 0.77; 95% CI, 0.41-1.46; P = 0.4238). In the IVT cohort, HDBAS was not associated with a 90-day mRS score (adjusted OR, 0.69; 95% CI, 0.31-1.56; P = 0.3742), the recanalization after 24 hours of onset (adjusted OR, 2.24; 95% CI, 0.47-10.78; P = 0.3132), and 90-day mortality (adjusted OR, 0.64; 95% CI, 0.26-1.57; P = 0.3264). Similarly, in the BMT cohort, HDBAS was not associated with 90-day mRS score (adjusted OR, 1.11; 95% CI, 0.47-2.63; P = 0.8152), the recanalization after 24 hours of onset (adjusted OR, 1.27; 95% CI, 0.40-4.02; P = 0.6874), and 90-day mortality (adjusted OR, 1.17; 95% CI, 0.46-2.96; P = 0.748). CONCLUSIONS: HDBAS may not be a reliable predictor of outcomes for patients with ABAO, regardless of whether they received EVT, IVT, or BMT.

Investigation of Nanoclay-Surfactant-Stabilized Foam for Improving Oil Recovery of Steam Flooding in Offshore Heavy Oil Reservoirs.

This study presents a study of nanoclay-surfactant-stabilized foam to improve the oil recovery of steam flooding in offshore heavy oil reservoirs. The foam stability and thermal resistance studies were first performed to investigate the influence of nanoclay on the stability and thermal resistance properties of the foam system. Then, the sandpack flooding tests were conducted for investigating the resistance factor and displacement abilities by nanoclay-surfactant-stabilized foam. The results showed that the nanoclay-surfactant-stabilized foam has excellent foaming ability and foam stability at 300 °C, which can be used in steam flooding for offshore heavy oil reservoirs. The resistance factor is greater than 30 at 300 °C when the gas-liquid ratio ranges from 1 to 3, which indicated that the nanoclay-surfactant-stabilized foam has good performance of thermal resistance and plugging effect. The heterogeneous sandpack flooding test showed that the nanoclay-surfactant-stabilized foam can effectively divert the steam into the low-permeability area and improve the sweep efficiency, thus improving heavy oil recovery of steam flooding. Therefore, the nanoclay-surfactant-stabilized foam flooding has a great potential for improving oil recovery of steam flooding in offshore heavy oil reservoirs.