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The existing models for calculating the water breakthrough time of gas wells in gas reservoirs with edge water ignore the effects of reservoir's interlayer heterogeneity, so their calculation results are more deviated from the actual water breakthrough time of gas wells. As a result, they cannot accurately and effectively guide the adjustment of gas well production system and the formulation of technical water control measures. In this paper, a water-flooding seepage experiment of parallel core was conducted by taking the gas reservoir with edge water of Lower Triassic Feixianguan Formation in the Puguang Gas Field of the Sichuan Basin as an example. Then, the effects of edge water inrush caused by the interlayer heterogeneity of reservoir on water breakthrough time of gas wells was analyzed by means of reservoir numerical simulation. Based on this, the inrush coefficient was introduced to characterize the interlayer heterogeneity of reservoir, and a model for calculating the water breakthrough time of gas wells in the commingled gas reservoir with edge water considering the influence of interlayer heterogeneity was established. Finally, five wells in the gas reservoir of Feixianguan Formation in the Puguang Gas Field were selected for case calculation. And the following research results were obtained. First, the interlayer heterogeneity of gas reservoir results in edge water burst. And the stronger the interlayer heterogeneity, the more severe the edge water coning and the sooner the water breakthrough. The water breakthrough time of gas wells depends on the water breakthrough time in the reservoir with the highest permeability. Second, a model for calculating the water breakthrough time of gas wells in the gas reservoirs with edge water considering the influence of reservoir interlayer heterogeneity is established based on the seepage theory. And the relative errors of its calculation results are in the range of −3.43–4.70%, which can satisfy the accuracy requirement of engineering errors. In conclusion, this newly established model can provide an effective method for accurately calculating the water breakthrough time of the gas well in the commingled gas reservoir with edge water. Furthermore, it is conducive to the adjustment of the production system of gas wells in the gas reservoir with edge water and the formulation of technical water control measures.

Water exists in shale gas reservoirs in the form of connate water and retained fracturing fluid. The nanoscale interaction between gas and water plays an important role in gas transport in shale na...

Condensate oil and water invasion coexist in the condensate gas reservoir with bottom water. Because of influences of condensate oil pollution and water invasion, gas recovery obviously decreases. ...

Complex fracture systems including natural fractures and hydraulic fractures exist in shale gas reservoir with fractured horizontal well development. The flow of shale gas is a multi-scale flow process from microscopic nanometer pores to macroscopic large fractures. Due to the complexity of seepage mechanism and fracture parameters, it is difficult to realize fine numerical simulation for fractured horizontal wells in shale gas reservoirs. Mechanisms of adsorption–desorption on the surface of shale pores, slippage and Knudsen diffusion in the nanometer pores, Darcy and non-Darcy seepage in the matrix block and fractures are considered comprehensively in this paper. Through fine description of the complex fracture systems after horizontal well fracturing in shale gas reservoir, the problems of conventional corner point grids which are inflexible, directional, difficult to geometrically discretize arbitrarily oriented fractures are overcome. Discrete fracture network model based on unstructured perpendicular bisection grids is built in the numerical simulation. The results indicate that the discrete fracture network model can accurately describe fracture parameters including length, azimuth and density, and that the influences of fracture parameters on development effect of fractured horizontal well can be finely simulated. Cumulative production rate of shale gas is positively related to fracture half-length, fracture segments and fracture conductivity. When total fracture length is constant, fracturing effect is better if single fracture half-length or penetration ratio is relatively large and fracturing segments are moderate. Research results provide theoretical support for optimal design of fractured horizontal well in shale gas reservoir.

In high-temperature, high-pressure (HTHP), water-soluble gas reservoirs, a significant amount of natural gas is dissolved in the formation water. During development, with changing reservoir pressure, the natural gas in the formation water will be released. The released natural gas will carry the formation water to form gas-liquid two-phase flow into the porous media of the gas reservoir, which results in premature water breakthrough, thus changing the law of formation water invasion. In order to determine the influence of water-soluble gas on formation water invasion, it is important to study the water-soluble gas content of water-soluble gas reservoirs. Based on experimentation and existing modeling, a prediction model was established for water-soluble gas content in HTHP water-soluble gas reservoirs, and the influence of water-soluble gas content on water invasion was studied. From the results, the following conclusions can be drawn. (a) The content of water-soluble gas increases with increasing pressure, first decreasing and then increasing with increasing temperature. (b) In addition to temperature and pressure, the factors affecting the content of water-soluble gas include the gas components and the mineralization degree of formation water. (c) The existing prediction model has the problems of large error and inconsistency with the measured value, (average error being 33.92%), especially lacking consideration of how changing carbon dioxide content in the gas composition affects the water-soluble gas content. (d) Considering the influences of temperature, pressure, gas components, and formation water mineralization on the prediction model of water-soluble gas reservoirs, the calculation results of the model are more in line with the actual circumstances of gas reservoirs, with the average error being 6.81% and the accuracy of water-soluble gas content prediction being increased five times. (e) Through case analysis, it is shown that the release of water-soluble gas has a great impact on the water breakthrough law of gas wells. Considering the water-soluble gas, the water breakthrough time of gas wells is relatively early. Results show that the water-soluble gas content prediction model for HTHP water-soluble gas reservoirs can predict the water-soluble gas content of water-soluble gas reservoirs more accurately, laying a foundation for understanding the water invasion law of water-soluble gas reservoir development and developing such a gas reservoir efficiently.

It is important that the tight gas reservoir is developed with test wells in the first place for the reasonable development, and it is necessary evaluation production index of test well. So, the paper will evaluate gas wells capacity, reasonable production, production decline law and producing reserves. Combining with calculation theory, comparison of adjacent wells and field practice, obtained reasonable production, production decline law and production reserves about test well, and through analysis the adjacent well obtained development experience and lessons about tight gas reservoir. The results show that the gas well development should pay attention to reasonable production and prevent energy falling too fast in tight gas reservoirs, The decline rule of wells with long production time should be analyzed by two stages. Through study, it will provide some reference and guidance for the development of gas wells in tight gas reservoirs.

A snake well is a complex well type and meanders in a sinusoidal pattern through multiple drainage areas provided by multiple isolated production zones. Conventional productivity calculation methods for horizontal wells could not be applied directly for snake wells because the production segments in the wellbore have large vertical fluctuation and wellbore pressure drop is noticeable. Starting from the distribution of velocity potential produced in an infinite reservoir by one snake well, this paper uses mirror image and the principle of superposition to obtain velocity potential and pressure distributions in bottom water drive reservoirs with and without gas cap, and edge water drive reservoir. Flow characteristics along the wellbore are then investigated and a pressure drop model is developed. Coupling the flow inside wellbore and in the reservoir, we developed and further solved a productivity prediction model for the snake well. The proposed approach to calculating well productivity better meets the reality and results in more accurate prediction. Case studies in bottom water drive reservoir with and without gas cap, and edge water drive reservoir show that snake wells with small fluctuation rates yield higher productivities than horizontal well. Also, permeability anisotropy has less impact on the productivity of snake well than that of horizontal well. For the reservoir with low vertical permeability, snake well can perform better than horizontal well.

Chunguang oilfield is a lithologic trap reservoir with edge water drive, whose horizontal well development effect is influenced by static factors and dynamic factors. In the process of production, the influences of static factors including reservoir physical properties and dynamic factors including working system, liquid production velocity on horizontal well development effects are different, and it is difficult to find main factor influencing horizontal well development effect with conventional single-factor analysis method. Combined with static and dynamic data of Chunguang oilfield, using multi-factor grey correlation analysis method, quantitative relationships between horizontal well development effect and different factors are systematically analyzed. Main factors influencing horizontal well development effect and dynamic influence laws between different factors and horizontal well development effect are clarified. Problems existed in the development process are known and it can provide the direction for future development and adjustment of Chunguang oilfield.