Logging Evaluation Method of Flow Units in a Dolomite Reservoir in the 4th Member of the Leikoupo Formation in Western Sichuan Gas Field

The dolomite reservoir of the 4th member of the Leikoupo Formation in Western Sichuan gas field primarily has highly-deviated wells and horizontal wells, and reservoir information is obtained principally by means of interval transit time and two-dimensional magnetic resonance imaging (NMR) logging data. Therefore, it is difficult to evaluate the reservoir and flow units. Based on the sedimentary facies, core experimental data, and reservoir comparison methods of key vertical wells, the reservoir of the 4th member of the Leikoupo Formation was divided into four types of flow units as determined by logging data. The pseudo-capillary pressure curve was constructed by NMR logging data. The high-fitness median pressure and displacement pressure were taken as intermediate parameters, and the coefficients of deviation degree (S index and T index) based on the median pressure and displacement pressure were established as parameters for quantitatively evaluating the reservoir’s pore structure. In addition, the classification criteria of the four types of flow units in the reservoir were established. The S index and T index were combined with porosity, permeability, and other parameters for continuously and accurately evaluating the pore structure of the dolomite reservoir along the horizontal wellbore and quantitatively distinguishing flow units. The logging evaluation method of flow units in the dolomite reservoir provides a technical reference for evaluation and development planning for horizontal wells in similar reservoirs.