1. Earth Science Institute,Northeast Petroleum University,Daqing 163318,China 2. Accumulation and Development of Unconventional Oil and Gas,State Key Laboratory Cultivation Base Jointly-constructed by Heilongjiang Province and the Ministry of Science and Technology,Northeast Petroleum University,Daqing 163318,China 3. No.5 Production Plant of Daqing Oilfield Company,PetroChina,Daqing 163513,China
In the previous Monte Carlo numerical simulation of compensated neutron logging, formation water salinity was mostly set at 0, but in fact, the alteration of formation water salinity would affect compensated neutron logging. In this paper, Monte Carlo method was used to simulate the influence of formation water salinity on compensated neutron logging, and its correction method was proposed. The relationship between salinity and counting rate, salinity and counting ratio, and the effect of salinity on the relationship between counting ratio and porosity and porosity sensitivity under different porosity conditions were simulated successively. According to the calculated results, under the same porosity condition, the counting rate decreases with the increase of salinity, and the counting rate of far detector decreases faster than that of near detector; the near-far counting ratio increases linearly with the increase of salinity as a quadratic function; based on a large number of simulation data, a bivariate function relationship between porosity and salinity is established for different formation water salinity conditions, which eliminates the influence of formation water salinity on compensated neutron logging. In addition, the sensitivity of porosity is obviously affected by salinity in medium and low porosity formations. The bivariate function relation between porosity and salinity established in this paper has completed the automatic correction of salinity effect, simplified the subsequent correction work related to formation water salinity effect, avoided complex instrument re-calibration, and provided a theoretical basis for accurate evaluation of reservoir porosity.
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Peng-Ju LI, Yong-Yong LI, Mao-He XU, Yong-Lu FU, Tian TIAN. A study of automatic correction method for the influence of formation water salinity on compensating neutron logging. Geophysical and Geochemical Exploration, 2019, 43(4): 815-821.
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