Probability distribution of reservoir parameters in the B oil field, Pearl River Mouth Basin

A block of the Pearl River Mouth Basin has a large trap area, irregular structure and limited well data and thus to get accurate reserve size, potential and risk, the probability method is most effective for rapid reserve assessment. The Z5 reservoir in the B oil field was taken as an example. Considering steep wings, long middle transition zone and the low level of well control, an area/thickness/shape factor method was used to construct a physical model of bulk-volume rock. N modules were divided according to the distribution form of reservoir. The form of Z5 reservoir was precisely described according to each module, which could reduce the influence of irregular structural form on reserve. Logarithmic normal distribution was used to analyze effective thickness and porosity. Normal distribution was chosen for oil saturation. A single value distribution model was adopted to study oil-bearing area, volume coefficient and crude oil density. The probability distribution of various reserve parameters and a reserve probability distribution model were established. The results show that the P_mean reserves of the approximate method were close to those of the deterministic method, and the error between them was less than 4%. Combined with reserve sensitivity analysis results of the geological parameters, the study could guide the studies of reserve sensitivity, economics, risk and potential, and provide a theoretical basis for development plans and decisions.