Productivity Of Fractured Horizontal Wells Research Articles

Optimizing tight oil extraction from low permeability tight reservoirs: a study on stress sensitivity effects and applications in carbon capture, utilization, and storage

This paper takes into consideration the impact of stress sensitivity on bioenergy production from low permeability tight reservoirs, focusing on the post-fracturing phase. This paper established a trilinear flow model that effectively takes into account the dynamics of such reservoirs. This model incorporates stress sensitivity parameters and uses the perturbation transformation and Laplace transformation to solve the productivity prediction formula. The final productivity prediction curve post-fracturing is achieved through a numerical inversion method. This study shows that the stress sensitivity effect significantly diminishes the productivity of fractured horizontal wells used in bioenergy extraction. By introducing stress sensitivity effect parameters, this paper manages to uncover the influence law of mobility and artificial fracture parameters on productivity. Notably, as the reservoir mobility increases, the cumulative bioenergy production from fractured horizontal wells improves significantly. In addition to the above, this paper also scrutinizes the sensitivity of artificial fracture parameters and optimize both the quantity and length of these fractures. This plays a crucial role in enhancing the productivity and efficiency of bioenergy extraction from these tight reservoirs. The applicability and reliability of this method are extensively tested, thereby establishing its potential in guiding the development of low permeability reservoirs post-fracturing. Importantly, this research sets the groundwork for combining bioenergy production with Carbon Capture, Utilization, and Storage (CCUS) technologies. By focusing on optimization and stress management in tight reservoirs, this paper contributes to the sustainable production of bioenergy and reduce carbon emissions, moving a step closer to a cleaner and sustainable future.

Productivity dynamic analysis of fractured horizontal well in ultra-low permeability reservoir

Daqing Oilfield is rich in low permeability reservoirs. In order to fully understand the development dynamics of ultra-low permeability reservoirs, this paper takes Daqing Oilfield as an example and studies the productivity dynamics of fractured horizontal Wells by numerical simulation method. The results show that the productivity of fractured horizontal Wells decreases exponentially with the decrease of formation permeability. The productivity of fractured horizontal well increases with fracture length and decreases with fracture spacing. With the increase of formation coefficient and reservoir thickness, the productivity increase of fractured horizontal Wells decreases. In the case of small well spacing, the smaller the formation coefficient and reservoir thickness, the higher the productivity of fractured horizontal Wells. Compared with conventional vertical Wells, fractured horizontal Wells have better production performance.

Calculation Method of Productivity for Shale Oil in Volumetric Fractured Horizontal Wells.

In order to evaluate quantitatively the productivity of shale oil in fractured horizontal wells and in view of the influence of non-Darcy seepage and pressure sensitivity on shale oil productivity, the methods of conformal transformation and superposition theory of complex potential are used to deduce the productivity formula in volumetric fractured horizontal wells with start-up pressure gradient and pressure sensitivity and to calculate quantitatively the productivity of each fracture. In addition, the influence factors on productivity, such as the fracture length, number of fractures, pressure sensitivity coefficient, starting pressure gradient, and other factors, have been analyzed as well. The study results indicate that the productivity of horizontal wells decreases with the increase of the start-up pressure gradient and pressure sensitivity coefficient. With the increase of the half-length and number of fractures, the productivity of fractured horizontal wells will increase, but the amplitude of increase decreases gradually. This method can be used for productivity calculation and optimization design of the fracturing parameter in volumetric fractured horizontal wells.

Performance Evaluation of Multistage Fractured Horizontal Wells in Tight Gas Reservoirs at Block M, Ordos Basin

Block M of the Ordos Basin is a typical low-permeability tight sandstone gas accumulation. To develop these reservoirs, various horizontal well fracturing technologies, such as hydra-jet fracturing, open-hole packer multistage fracturing, and perf-and-plug multistage fracturing, have been implemented in practice, showing greatly varying performance. In this paper, six fracturing technologies adopted in Block M are reviewed in terms of principle, applicability, advantages, and disadvantages, and their field application effects are compared from the technical and economic perspectives. Furthermore, the main factors affecting the productivity of fractured horizontal wells are determined using the entropy method, the causes for the difference in application effects of the fracturing technologies are analyzed, and a comprehensive productivity impact index (CPII) in good correlation with the single-well production of fractured horizontal wells is constructed. This article provides a simple and applicable method for predicting the performance of multi-frac horizontal wells that takes multiple factors into account. The results can be used to select completion methods and optimize fracturing parameters in similar reservoirs.

Integrated Simulation for Hydraulic Fracturing, Productivity Prediction, and Optimization in Tight Conglomerate Reservoirs

With the development of advanced horizontal drilling and multistage hydraulic fracturing techniques, the productivity of unconventional tight oil such as that found in the Baikouquan Formation of the Mahu Sag in the Junger Basin has been increasing. The Mahu oilfield is the largest tight conglomerate reservoir in the world. However, predicting the productivity of fractured horizontal wells in tight oil remains a challenge due to the high heterogeneity of the reservoir and complexity of its hydraulic fractures. Therefore, this study proposes a workflow for coupled geological modeling, along with fracturing and reservoir simulations in tight conglomerate reservoirs. Taking well block Ma131 as an example, a three-dimensional geological model is first built according to the results of geophysical research. The unconventional fracture modeling is used next to establish a fracturing simulation. Given the lack of natural fractures and the high concentration of conglomerate in the study area, the method of the multiple groups of microscale natural fractures is used to simulate the impact of gravel on fracture propagation. The feasibility of the method is verified with microseismic monitoring data and treating curves. Thereafter, an unstructured grid and the INTERSECT reservoir simulator are used to simulate the production performance of horizontal wells. The stress sensitivity effect of the rock matrix and fractures and the changes in the formation flow field caused by fracturing are considered in the reservoir simulation. Hydraulic fractures are found to be unable to form complex fracture networks easily under the conditions of high stress difference, high gravel content, and undeveloped natural fractures. However, they show the characteristics of macroscopic simplicity and local branching. Reducing cluster spacing can increase the complexity of hydraulic fractures and the productivity of horizontal wells. Finally, the proposed integrated simulation process is used to optimize well spacing, fracturing stimulation parameters, and the production system. Overall, the study serves as a guide for maximizing the production and economic benefits of tight conglomerate reservoirs.

A semi-analytical model for investigating the productivity of fractured horizontal wells in tight oil reservoirs with micro-fractures

Combining horizontal drilling with hydraulic fracturing has become a well-established technique to improve well productivity in tight oil reservoirs. The existence of micro-fractures in these reservoirs affects the fluid flow process as well as the productivity. However, current models for evaluating the well performance of fractured horizontal wells containing micro-fractures lack accuracy. Hence, the objective of this study is to build an efficient model to analyze well productivity, considering the effects of micro-fractures. A novel flow model for multi-fractured horizontal wells was established, considering the effect of micro-fractures on the fluid flow. Subsequently, we built a reservoir model based on the typical fracture and fluid properties of a tight oil block in the Daqing oil field, China. Good agreement between the prediction results and field data was obtained, indicating that the effect of micro-fractures on well productivity cannot be neglected. Further study reveals that micro-fractures essentially function as a joint connecting reservoir matrix and have a persistent impact on well productivity. Micro-fractures can promote well productivity; however, if the value of micro-fracture permeability increases, this promotional effect will slow down. Well productivity can be considerably improved as an increase in micro-fracture percentage. Finally, a series of sensitivity studies were conducted to identify the effects of critical parameters on well productivity. Results show that reservoir permeability significantly influences well productivity, followed by reservoir effective thickness, micro-fracture percentage, fracture number, hydraulic fracture half-length. Pressure sensitivity coefficient, threshold pressure gradient and micro-fracture permeability have the least effect on well productivity. This work provides a sophisticated and efficient tool to evaluate the productivity of multi-fractured horizontal wells in tight oil reservoirs with micro-fractures.

The new method on gas-water two phase steady-state productivity of fractured horizontal well in tight gas reservoir

Based on a large number of tight gas exploration and development literature researches, it is found that the horizontal drilling technology and fracturing operation are usually used in the tight gas reservoir for its low permeability. Three tasks have been done in this paper. First, we described the characteristics and the flow mechanism of the tight gas reservoirs which are different from the conventional ones and gave a new definition of two phase pseudo pressure. Second, formation stress sensitivity, starting pressure gradient and the interaction of fractures are considered. Equivalent flow resistance was used to establish a model of tight gas steady flow, and a new productivity formula of fractured horizontal well in tight gas reservoir derived by the new flow model. Third, the productivity influence research has been done, which gives the influence degree of different parameters. It is signified that the productivity will increase with the addition of the permeability modulus and decrease with the increase of the water-gas volume ratio. The influence of starting pressure gradient was not very clear and the fractures parameters showed the opposite situation. Therefore optimization design of tight gas reservoir development mode can be improved by the productivity formula and research. Cited as : Li, X., Liang, J., Xu, W., et al. The new method on gas-water two phase steady-state productivity of fractured horizontal well in tight gas reservoir. Advances in Geo-Energy Research, 2017, 1(2): 105-111, doi: 10.26804/ager.2017.02.06

Pressure-Transient Characteristics of Hydraulically Fractured Horizontal Wells in Shale-Gas Reservoirs With Natural- and Rejuvenated-Fracture Networks

Summary During the past few years, several studies have analyzed the pressure-transient responses of hydraulically fractured horizontal wells in shale-gas reservoirs. However, that research included simplified models that reflected natural and hydraulic fractures -only, unlike real shale reservoirs. To develop an accurate shale-gas model, this study considers the effects of rejuvenated fractures as well as natural and hydraulic fractures. Rejuvenated fractures, regarded as an important specificity in this paper, are revitalized natural fractures created by hydraulic fracturing. To analyze the pressure-transient characteristics and productivity of fractured horizontal wells in shale reservoirs, extensive numerical simulations have been conducted. This model considers the effects of natural- and rejuvenated-fracture permeability, matrix permeability, parameters of hydraulic fractures (e.g., width, height, and half-length), and the range of stimulated reservoir volume. Results show a clear distinction between existing models and the proposed model. In the proposed model, the boundary induced by the rejuvenated fractures generates pseudoboundary-dominated flow. This work expands our insight into the pressure-transient characteristics of a hydraulically fractured horizontal well in a shale-gas system.

Influence of Fracture Parameters on the Productivity of Fractured Horizontal Well Based on Fluid Mechanics in Tight Gas Reservoir

Multiple fractures are needed by hydraulic fracturing in order to improve the horizontal well productivity of a single well in tight gas reservoir. The calculation accuracy of productivity influences on the fracturing optimization results and the success ratio and effectiveness of fracturing treatment. This work focuses on analyzing the influence of fracture parameters on fractured horizontal well productivity in tight gas reservoir through establishing a productivity prediction model of fractured horizontal well, considering the interference between fracture and fracture and the wellbore pressure drop. Results show that the fracture parameters, such as fracture number, fracture interval, fracture conductivity and fracture length, have different influences on the productivity of fractured horizontal well and thus, the effects of fracture parameters should be taken into account when designing the fracturing treatment.

Productivity and Drainage Area of Fractured Horizontal Wells in Tight Gas Reservoirs

Summary This paper discusses the performance and productivity of fractured horizontal wells in heterogeneous, tight-gas formations. Production characteristics and flow regimes of unfractured and fractured horizontal wells are documented. The results show that if hydraulic fracturing affects stress distribution to create or rejuvenate natural fractures around the well, the productivity of the system is significantly increased. Unless there is significant contrast between the conductivities of the hydraulic and natural fractures, hydraulic fractures may not significantly contribute to the productivity. For extremely tight formations, the effective drainage area may be limited to the naturally fractured region around the well and the hydraulic fractures. It is also shown that very long transient flow periods govern the productivity and economics of fractured horizontal wells in tight formations. The results of this study are also applicable to oil production from fractured shale.

A new method for prediction of productivity of fractured horizontal wells based on non-steady flow

Hydraulic fracturing technologies of horizontal well are important ways to develop oil-gas field with low permeability. Productivity forecast of fractured horizontal wells is a difficult problem of hydraulic fracturing technologies. Basing on non-steady flow of fractures fluid during production, applying potential function principles, superposition principle and mathematical method for solving, coupling of seepage flow in the formation and pipe flow in the well bore, a new model on multi-fracture interference productivity forecast of fractured horizontal well is established in this article. The results indicate the coincidence rate between this model and practice is high. The pressure loss in the horizontal well bore has definite influence on the production status of fractured horizontal wells. The productions of different fractures in horizontal well bore are unequal, the productions of outer fractures are higher than middle fractures ; the pressure in the well bore shows an uneven distribution, the pressure declines gradually from finger tip to heel end. Asymmetry of fractures may make productivity of fractured horizontal wells decline. The conclusions are instructive in designing fractured horizontal well for low permeability reservoir.