We present a new stochastic method of reconstructing porous medium from limited morphological information obtained from two-dimensional microimages of real porous medium. The method is similar to simulated annealing method in the capability of reconstructing both isotropic and anisotropic structures of multiphase but differs from the latter in that voxels for exchange are not selected completely randomly as their neighborhood will also be checked and this new method is much simpler to implement and program. We applied it to reconstruct real sandstone utilizing morphological information contained in porosity, two-point probability function and linear-path function. Good agreement of those references verifies our developed method's powerful capability. The existing isolated regions of both pore phase and matrix phase do quite minor harm to their good connectivity. The lattice Boltzmann method (LBM) is used to compute the permeability of the reconstructed system and the results show its good isotropy and conductivity. However, due to the disadvantage of this method that the connectivity of the reconstructed system's pore space will decrease when porosity becomes small, we suggest the porosity of the system to be reconstructed be no less than 0.2 to ensure its connectivity and conductivity.

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Production sharing contract (PSC) is one of the most commonly used contract type in international petroleum cooperation practices, under which, contractors obtain net reserves composed of in kind “cost oil” and “profit oil” by taking risks, bearing exploration, development and production costs, paying royalties, income taxes and other fees to the government of the resource country (the host government). The net reserves owned by a contractor refer to the remaining economic recoverable reserves that the contractor can obtain during the remaining contract period, which represent the real revenue the contractor can realize. Taking Project XX in Africa for example, this paper analyzed the methods for estimating net oil and gas reserves under PSCs, discussed the impacts of production, decline rate, plan, prices, costs, profit oil sharing and taxes on net reserves from four aspects including technique, economics, commerciality and engineering. In addition, the paper also made sensitivity analysis of the factors having significant influence on net reserves, such as the oil production, oil prices, operation expenses and investment, and put forward some recommendations for optimizing field development strategies to maximize contractors’ economic benefits.

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