A twenty-year follow-up study was carried out at Baiyun Obo Rare-earth Iron Mine in China, This mine has been mined since 1958. Its ore contains 0.04% of ThO 2 and 10% of SiO 2 . The purpose of this study is to investigate possible health effects in dust-exposed miners following long-term exposure to thorium-containing dusts and thoron progeny. By using the negative high voltage exhaled thoron progeny measurement system to estimate the miner's thorium lung burden. The highest thorium lung burden among 1 158 measurements of 638 miners was 11.11 Bq. The incidence of stage 0 + pneumoconiosis was increased among dust-exposed miners. An epidemiological study showed that the lung cancer mortality of the dust-exposed miners was significantly (p < 0.005) higher than that of the non-exposed group. It is suggested that the difference results in the long-term exposure to thorium-containing dusts (carcinogens are ThO 2 and SiO 2 ) and thoron progeny. This is the first evidence in humans of the carcinogenicity after long-term inhalation of thorium-containing dusts and thoron progeny. The total person-years of observation for the dustexposed miners and the controls were 62 712 and 34 672 respectively. (1993.12.15-1994.12.15), a project from IAEA Project no. 11526 RBF (2000RBF ( .12.15-2001 RÉSUMÉ
There are serious drilling fluid loss problems in fractured reservoirs during drilling and completion. Indoor evaluation of the drilling fluid lost control effect is an important basis for on-site plugging formula design, but there are some problems in drilling fluid lost control evaluation, such as the inability to evaluate specific loss types. Therefore, based on the classification of loss causes, this paper defines the main control factors of drilling fluid lost control efficiency of different loss types and puts forward a method for recognizing loss types. The influence of fracture module and experimental steps on the drilling fluid lost control efficiency was evaluated through laboratory experiments. Based on the analysis method of indoor and field drilling fluid lost control efficiency, the best laboratory experimental conditions of different loss types were recommended, and then, the experimental evaluation method of the drilling fluid lost control efficiency considering various loss types was established. This method can comprehensively evaluate and grade the lost control ability of the plugging formula. Through the verification in Block K of the Tarim Basin, the test results are closer to the field lost control results, and the evaluation results of the drilling fluid lost control efficiency are better, which can guide the field leakage control evaluation.
Gas lift operations are highly dependent on data quality and team competence to operate the asset efficiently. Traditional methods for gas lift well surveillance and diagnostics rely on wireline services, a method with growing constraints to adapt to constantly evolving well and operational challenges. The Well Intervention-less Tracer Surveillance System (WITSS) provides a cost effective, comprehensive approach to well surveillance without the reliance on tools entering the well. This results in reduced HSE risks and no associated deferred production. This paper describes a pilot implementation to evaluate the adequacy and accuracy of this technology in the context of ADNOC Onshore gas lift producers. The objective is to evaluate its performance against conventional method data sets and assess the reproducibility of data where no reference existed. The 10 well pilot included both accessible and obstructed wells. Data from the custom designed modular portable kit used for executing the surveillance activities, was analyzed and compared against conventional flowing gradient surveys with full data consumption in well models for comprehensive nodal analysis and opportunity identification. For this pilot, ten wells were surveyed twice using the WITSS method. Results were compared to traditional methods acquired through wireline surveys for accessible wells, and against established multi-phase flow correlations for obstructed wells. The pilot confirmed the WITSS method is as accurate as conventional gauge measurements in mapping pressure and temperature profiles in gas lifted wells. The WITSS method provided additional insight on accurate gas consumption based on the assessment of total gas lift utilization per well and allowed comprehensive model calibration and well performance definition. It also identified potential integrity issues via identification of primary injection at designed stations and secondary unwanted injection sites. Continuous compositional gas analysis of both injected and produced gas streams provided additional verification for analyzing gas lift injection performance. It also highlighted a change in fluid compositional analysis opening discussions for material selection review of the assets. Production uplift identified from 50% of wells was compliant with the reservoir management strategy. The value proposals of flow stabilization through gas lift valve re-calibrations and replacements, adjustment of injection flow rate and further controls on injection pressure management are under process for implementation. Full field scale up scenario is under preparation.
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