| At present, onshore oilfield has entered the mining later period, the variation ofremaining oil can be detected in time, enhance oil recovery has become an importanttopic. Carbon/Oxygen spectral log can penetrate metal casing and detection thevariation of remaining oil in stratum, at the same time provide rich stratuminformation, and provide more information for oil-field development.This paper mainly using Monte Carlo method to study in the loggingenvironment the ratio of carbon to oxygen and calcium silicon ratio is influent by,logging instrument for neutron shielding material selection and Source from theground, shielding thickness instrument structure for neutron shielding effect; and thestructure of the instrument, the fluid in the well, wellbore radius to gamma spectrum.With the use of Monte Carlo method, we had simulated and researched theneutron shielding effectiveness of different thickness of W, Cu, Cd, B4C andpolythene mixture, Ag and Al under the condition of logging environment, andcomparing kinds of shielding design scheme in neutron shielding effect. The resultshows that mixed shielding materials better than multi-layer and a single shieldingmaterials shielding in neutron shielding aspects; tungsten is the best in the singleshielding materials, on the same thickness, when taking B4C and polythene mixtureas the shielding material, the counts of1keV-1MeV neutron are the least; copper andtungsten respectively mix with the B4C and polythene mixture, tungsten mixture inneutron shielding is slightly better than the mixture of copper materials in neutronshielding, copper mixed materials more economic and practical.Using Monte Carlo numerical simulation analyze in the different source distancethe fluid from the well, borehole radius, the distance of the shaft well logging tool,casing thickness, mud cake thickness the influence to logging carbon/oxygen ratio and C/S ratio. All factors taken into consideration, the optimal short spacing of C/Ologging tool for20cm to25cm can reflect in well fluid, casing thickness, and Strataporosity; the optimal long spacing is between40cm to45cm. The casing pipe bestthickness of0.78cm, the carbon and oxygen of inelastic scattering ratio candistinguish the fluid Low porosity stratum. |
