The Longwangmiao Formation gas reservoir in the Moxi block of the Sichuan Basin is a complex carbonate reservoir characterized by a low porosity and permeability, strong heterogeneity, developed natural fractures, and active water bodies. The existence of natural fractures allows water bodies to easily channel along these fractures, resulting in a more complicated mechanism and dynamic law of gas-well water production, which seriously impacts reservoir development. Therefore, a core-based simulation experiment was designed for oil–water two-phase flow. Three main factors influencing the water production of the gas reservoir, namely fracture permeability, fracture penetration, and water volume multiple, were analyzed using the orthogonal test method. The experimental results showed that the influences of the experimental parameters on the recovery factor and average water production can be ranked as water volume multiple > fracture penetration > fracture permeability, with the influence of the water volume multiple being slightly greater than that of the other two parameters. It provides a certain theoretical basis for water control of the gas reservoir.

In Tahe Oilfield, Tarim Basin, NW China, although the carbonate reservoir displays poor porosity and permeability in matrix, the fractured-vuggy system distributes in a random, discreet and discontinuous way, which could yield high oil rates once the fractured-vuggy system is connected by production wells. The fractured-vuggy carbonate reservoirs consist a group of large caves which are inter-connected with high permeable fractures. Due to the lack of powerful and suitable IOR (Improved Oil Recovery) strategies, the depletion recovery is usually applied at the beginning for a fractured-vuggy carbonate reservoir. During the depletion process, the elastic energy of the cave formation starts to decrease, which will cause insufficient liquid supply. Then, the water was injected to improve the oil recovery when the energy (pressure) is the main reason for the insufficient production performance of the well. However, if the high water cut is the main reason, alternative IOR techniques such as the N-2 huff and puff method could be utilized. This paper mainly researches the application of N-2 huff and puff in a fracture-vuggy carbonate reservoir, where the critical parameters for designing the N-2 huff and puff process are proposed. In addition, the proposed method is applied to Well SX to serve as a practical example. Based on the three-dimensional (3D) quantitative sculpture geological model and the dynamic production analysis, the critical parameters for N-2 huff and puff are obtained by numerical simulation. In addition, the obtained parameters are validated by the field data, which proves that the proposed method can be applied to design the critical parameters for simulating the N-2 huff and puff process in a fractured-vuggy carbonate reservoir.

In Tahe Oilfield, Tarim Basin, NW China, the carbonate reservoir displays poor porosity and permeability in its matrix, while the fractured-vuggy system is distributed in a random, discreet and discontinuous way, which yields significant oil rates once the fractured-vuggy system is connected by production wells. The fractured-vuggy carbonate reservoirs are consisting of a group of large carves and inter-connected by high permeability fractures. Due to lack of powerful and suitable EOR (Improved Oil Recovery) strategies, depletion-drive recovery is commonly adopted for practical production at the beginning. After a period of production, the elastic energy of the cave formation weakens, causing insufficient liquid supply, the water injected for water flooding is used to improve the oil recovery of the fractured-vuggy carbonate reservoirs. However, the water injection curves of the carbonate reservoir are different from that of the sandstone reservoir as their fundamental flow mechanisms are different. For the fractured-vuggy reservoirs with high permeability, the water injection curves can be adopted to calculate the volumes in place of crude oil and formation water in a single or multi-caves. This paper presents a new model of injection curves. Using the proposed model with multi-round water injection curves, we can initially judge reservoir type and determine the volumes of cave, crude oil and water in the caves reasonably. Besides, as testified by the practical case, the parameters interpreted by the new models are proved to be reasonable and reliable. This new model is a useful tool to estimate the crude oil reserves, to demonstrate how much remaining oil in the caves, and to identify where the water-oil contact is.

The interwell interference often affects the accuracy of the prediction results of water breakthrough time in a bottom water reservoir with smaller well spacing. Based on superposition principle of potential function, a new prediction formula considering the phenomenon of well interference is set up to explore the effects of the distance between adjacent wells and oil well production on water breakthrough time. The results show that smaller distance and greater oil well production would cause bigger interference and earlier water breakthrough time. The influence of the output and well spacing of the well on the water breakthrough time of the well decreases with the increase of the well spacing.

针对桥上无缝线路小阻力扣件进行大量纵向阻力的试验研究,设计多功能纵向阻力试验台,分别进行不同胶垫类型、螺栓扭矩和有无竖向载荷情况下的扣件纵向阻力试验,研究扣件阻力的影响规律。结果表明:不同类型的胶垫对扣件阻力的影响较大;在无载状态时扭矩对扣件阻力的影响为线性关系,有载时则不然。