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Design and optimization of well spacing is a key indicator for evaluating the development effect of shale gas reservoirs. On the basis of theoretical understanding, and after the verification by analogy, numerical simulation, and economic evaluation, a complete workflow from inter-well interference simulation and dynamic data diagnosis to multi-well production simulation and well spacing optimization was formed. First, a pressure detection boundary propagation model is established to simulate the response degree of inter-well interference under different connected conditions. Second, inter-well interference is identified and diagnosed depending on the inter-well interference response behaviors and the interpretation of performance data from gas wells. Third, taking the geological interpretation and dynamic analysis results as basic parameters, a multi-well numerical model for volume fracturing in gas reservoirs is established to simulate the production performance of gas field, and then well spacing is optimized in combination with the net present value model. The application in the Ning 201 well block in the Changning National Shale Gas Demonstration Area has shown that a smaller well spacing can allow a premature inter-well interference and also the enhancement of recovery in the entire block. Given the current fracturing scale and parameter system, the well spacing of 300–400 m can be optimized to 260–320 m, that is, the number of wells per unit area increases by 20%–30%. As a result, the recovery percent of reserves in the block increase by about 10%. The net present value of the block rises, but the corresponding optimal well spacing does not change, with the production period.

Instead of traditional analysis, net present value analysis can convert the future benefits and costs to their value today, so it reflects the actual economical condition better. Under the assumptions of the base case, the net present value of the Wetland Reservoir Subirrigation System (WRSIS) investment is 885,000Yuan(59,000Yuan/acre), which show that the system has high economic value to farmers and a good prospect to be widely used in China.

This study compares incentive effects of various tax depreciation methods currently adopted in European transition economies. In these countries straight-line, geometric-degressive and accelerated depreciation measures are quite popular in combination with different corporate tax rates. Their generosity is determined on the basis of Samuelson's true economic depreciation. For this purpose, the present value model is applied under the particular consideration of different financial structures. In this context the traditional Modigliani-Miller theorem for capital structure is revisited. Furthermore, the aspect of inflation is integrated into the model. The central issue is that the historical cost accounting method generally applied for the calculation of the corporate tax base causes fictitious profits in inflationary phases that are also taxed. Therefore, in an inflationary period generous tax depreciation provisions do not promote private investment as designed, but partly compensate such additional tax burdens caused by inflation.

This study compares incentive effects of various tax depreciation methods which are currently employed in selected OECD countries. Their generosity is determined on the basis of Samuelson's true economic depreciation. For this purpose, the present value model is applied. The central issue is that the so-called historical cost accounting method, which is adopted in practice when calculating the corporate tax base, causes fictitious profits in inflationary phases that should also be taxed. Therefore, in periods with inflation generous tax depreciation provisions do not adequately promote private investment as designed, but partly compensate such losses caused by inflation.

Subirrigation in conjunction with an artificial wetland has been shown to benefit the environment. It must also be demonstrated that this technology can be profitable for the private sector. Using cost structures developed from three Northwest Ohio test sites, this paper examines the economic soundness of applying these techniques to production agriculture. The hypothesis is that the benefits of increased yields resulting from stabilizing the water supply throughout the growing season will offset the costs of construction. Presented results will include a summary of private revenues and costs associated with the subirrigation and artificial wetland investment for the three demonstration sites.