| The most economical and direct method of evaluating oil and gas characteristics and productivity in reservoirs is to detect the oil and gas content which drilling fluid carry out from the reservoir while drilling.The gas logging technique has been able to detect the gas components and gas content in drilling fluid at present.However,some oil and gas detection qustions need to be solved during drilling.Those are how to detect the oil content in drilling fluid while drilling,and how to discover the real oil reservoirs when the high grade fluorescence of additives in drilling fluid masked the original fluorescence indicator of cuttings from drilling.Low-field nuclear magnetic resonance(NMR)technique is capable of detecting oil cintent in drilling fluid,but the use of laboratory NMR measuring instruments can not analyze the drilling fluid on line,and the discrete analysis data does not represent the actual reservoir oil data.Base on the above requirments,drilling fluid NMR online analysis technology was studied in this thesis.The online drilling fluid NMR analyzer with relaxation reagent added automatically was designed and implemented,and the instrument has been performed the well site trials.The theory and method of drilling fluid NMR analysis are studied.In the laboratory,a variety of types of drilling fluid samples and common fluorescent additives are analyzed,and the method of oil content detection in drilling fluid is studied.For the complex drilling fluid,the influence of oil and water signals is analyzed when the Mn Cl2 relaxation reagent adding into drilling fluid.These researches not only verify the previours researches but obtain some new acquaintances.Combined with the conditions of drilling site,The method of the drilling fluid pretreatment and adding relaxation reagent into drilling fluid was put forward,and the instrument which can obtain drilling fluid sample quantitatively and continuously and automatically add the relaxation reagent are designed.The high performance NMR sensor for drlling fluid analysis is designed.The NMR sensor's structure with 2 sets of double magnetic rings are designed and implemented through the simulation analysis,and the NMR antenna with high gain and high quality factors is developed.The weight of the NMR sensor is about 20kg,and the resonance frequency is about 20 MHz,and the inner magnetic field is homogenous.The linearity correlation of test result with standard NMR sample is 0.998.The NMR sensor can detect the oil content of 40ppm,this number is the minimum oil content which can discrible the oil-bearing reservoirs as fluorescence grade.The NMR measurement and control spectrometer is studied.It mainly consists of analog circuit and the digital circuit.The parameters of each circuit are cacluated,and the modules of circuit are devoleped such as multistage amplification circuit,sequential control circuit and isolation control circuit,etc.According the test results,the NMR spectrometer has the amplification output power of 300W and the radio frequency of20MHz,which fulfils the requirements of NMR sensor measurement and control.The online NMR detection instrument for drilling fluid is developed through analyzing the standard of instrument application and the drilling fluid analysis process at well site.Auto-sampling device takes samples of drilling fluids continuously and mixs relaxation reagent into drilling fluid automatically and quantitatively pumps the sample into the drilling fluid analysis for analysis.Finally,after analysis,the drilling fluid sample is pumped to the pit for recycling.The online NMR detection instrument for drilling fluid can be installed near the outline of drilling fluid,and used the TCP/IP protocol to transmit the data and remote control.The online NMR instrument for drilling fluid has been tested and applied at the drilling well site in oil field and successful 100%discover the oil-bearing reservoirs.The application results are excellence. |
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