Some wellbore segments have little or no contribution to total production rates because of reservoir heterogeneity, completion methods, and nonuniform formation damage along the horizontal wellbore. This work presents a semianalytical approach to determine the effective producing length (EPL) and production distribution of horizontal well, and further estimate the locations of malfunctioning horizontal wellbore and the segments of water or gas coning through the history matching of bottomhole-pressure (BHP) data. In this approach, horizontal wellbore was divided into multiple producing segments and each producing segment (PS) can be considered as a cylindrical source. New pressure-transient solutions are further developed for a horizontal well with multiple segments of arbitrary length, production, skin factor, and spacing. This work obtaines the type curves and further investigates the effect of crucial parameters (e.g. EPL, spacing between PS, number, production and skin factor of each PS) on pressure-transient behaviors. Results show that there are distinct differences among type curves with different parameters above. A horizontal line with the value of 0.5/N can be noticed in the pressure-derivative curve during the second radial-flow regime when inteferences between PS are minor. If the second radial-flow was misinterpreted as pseudoradial-flow, the interpreted permeability will be N times smaller than the accurate result. Therefore, it is significant to identify the horizontal line correctly especially for low-permeability reservoir (hard to reach the second radial-flow) and offshore oil fields (because of the short testing time). Finally, a history matching procedure is developed to determine the parameters above, and has been applied into two horizontal wells of Hudson oilfield in Tarim Basin. Case studies highlight the physical consistency of the solution, and demonstrate its practicability to estimate the EPL and diagnose the locations of malfunctioning horizontal wellbore. The approach proposed in this work can be used to evaluate formation and well performance along horizontal wellbore so that engineers could make decisions on field strategies to improve well performance.

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Abstract. Vacuum combined with surcharge preloading has been widely used in China recent years. However, the mechanism of vacuum combined with surcharge preloading method is still not clear. This paper expounds the mechanism of vacuum combined with surcharge preloading. Engineering application technology in highway including design method and filling processing of roadbed are also explained. Ground settlement, stratified settlement, pore water pressure and deep horizontal displacement monitoring can reflect the stress and strain of the foundation. Results of deformation monitor is very important to guide the filling speed of roadbed. The bearing capacity of foundation are improved after the action of vacuum combined with surcharge preloading. Engineering applications results show that vacuum combined with surcharge preloading method has achieved good benefits in the treatment on soft foundation in highway.