Gas flow rate evaluation in coal coupling the matrix shrinkage effect caused by water extraction

2021 ◽  
pp. 1-20
Author(s):  
Yanan Miao ◽  
Chaojie Zhao ◽  
Gang Zhou
Keyword(s):  
Relative Humidity ◽  
Flow Regime ◽  
Production Rate ◽  
Water Extraction ◽  
Linear Flow ◽  
Matrix Shrinkage ◽  
Well Production ◽  
Shrinkage Effect ◽  
The Matrix ◽  
Coal Reservoir

Abstract Estimating production in coal accurately is crucial for promoting the process of safe, efficient and green coal mining. It has been gradually recognized that horizontal wells with multiple fractures are employed to develop the coal reservoir, which signifies that the linear flow regime will dominate for a rather long time. However, the traditional analysis approaches of transient linear flow regime may yield the overestimation of coal reservoir property. In this work, a new analytical model was proposed to estimate the rate-transient of wells with multi-fractures in coal reservoir that produce at a constant flowing-pressure, which takes multiple flow mechanisms into consideration. Especially, the matrix shrinkage effect caused by water extraction from microscopic pores was incorporated, which has never been investigated by current production analysis models. In comparison with the conventional reservoir, the advanced pseudo-pressure and pseudo-time equations incorporating above critical mechanisms were established, including the four effects of gas slippage, effective stress, and matrix shrinkage caused by gas desorption/water extraction. In addition, the excellent agreement between the predicted rate by the proposed model and field data was achieved to validate the reliability of proposed models. Furthermore, the sensitivity analysis was carried out to clarify the influence of a series of factors on the seepage mechanism and productivity curve. Results demonstrated that the matrix shrinkage effect caused by water extraction may increase the well production rate in coal reservoir. Selecting one field case as an example, the production rate predicted by the red curve is obviously higher than that by the green curve, the average discrepancy yields around 39.5%. The relative humidity in coal matrix will present a positive impact on well production performance. Taking a field case as an instance, when the relative humidity varies from 8% to 14%, the well production sharply increases by about 11.6%.

A Permeability Model for Undersaturated Coalbed Methane Reservoirs Considering the Coal Matrix Shrinkage Effect

2013 ◽  
Vol 807-809 ◽  
pp. 2413-2420 ◽  
Author(s):  
Jun Long Zhao ◽  
Da Zhen Tang ◽  
Hao Xu ◽  
Yan Jun Meng ◽  
Yu Min Lv
Keyword(s):  
Pore Pressure ◽  
Coalbed Methane ◽  
Well Test ◽  
Dynamic Prediction ◽  
Permeability Model ◽  
Matrix Shrinkage ◽  
New Model ◽  
Shrinkage Effect ◽  
The Matrix

With the analysis of key elements on the strain state of coal, a permeability dynamic prediction model which is divided by the critical desorption pressure for undersaturated coalbed methane (CBM) reservoirs was established on the basis of pore pressure and considering the matrix shrinkage effect of coal. The law between permeability and pore pressure was analyzed during production with the new model. Through case study, the rationality of the model was also verified. The research shows that the degree of permeability changes mainly depends on the relationship between the critical desorption pressure and the rebound pressure which depends on the strength of the matrix shrinkage. Under the condition of equivalent matrix shrinkage, the reservoirs permeability rebounds better with high Young's modulus and low Poisson's ratio. Adjustment factor contributes to improve the influence of matrix shrinkage on permeability and the larger the matrix shrinkage strength is, the higher the permeability rebounds. PM model and CB model are similar to the new model. PM model limits the matrix shrinkage strength, and CB model is a special case of the new model. Comparing with the well test permeability, the new model is more reasonable to characterize the matrix shrinkage effect in the development process.

scholarly journals The Effects of Exchange Flow on the Karst Spring Hydrograph under the Different Flow Regimes: A Synthetic Modeling Approach

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1189
Author(s):  
Malihe Shirafkan ◽  
Zargham Mohammadi ◽  
Vianney Sivelle ◽  
David Labat
Keyword(s):  
Flow Regime ◽  
Spring Discharge ◽  
Exchange Flow ◽  
Flow Conditions ◽  
Spring Hydrograph ◽  
Conduit Flow ◽  
Discharge Fluctuations ◽  
Recession Coefficient ◽  
The Matrix ◽  
Synthetic Modeling

In this study, a synthetic modeling approach is proposed to quantify the effect of the amount and direction of the exchange flow on the karstic spring discharge fluctuations under different hydrologic conditions corresponding to high and low flow conditions. We hypothesis that the spring discharge fluctuations constitute a valuable proxy to understand the internal processes of the karst system. An ensemble of spring hydrographs was synthetically produced to highlight the effect of exchange flow by exploring the plausible range of variability of coefficients of exchange flow, conduit diameter, and matrix hydraulic conductivity. Moreover, the change of the rate of point recharge through the karst conduit allows for the quantifying of the sensibility of the spring hydrograph to the directions of exchange flow. We show that increasing the point recharge lies to a remarkable linear recession coefficient (β) as an indication of the conduit flow regime. However, a reduction in and/or lack of the point recharge caused the recession coefficient to change to exponential (α) due to the dominant effect of the matrix restrained flow regime and/or conduit-influenced flow regime. The simulations highlight that the exchange flow process from the conduit to the matrix occurred in a short period and over a restricted part of the conduit flow regime (CFR). Conversely, the exchange flow dumped from the matrix to the conduit occurs as a long-term process. A conceptual model is introduced to compare spring hydrographs’ characteristics (i.e., the peak discharge, the volume of baseflow, and the slope of the recession curve) under the various flow conditions with the directions of the exchange flow between the conduit and the matrix.

scholarly journals Production Optimization for Natural Flow and ESP Well A Case Study on Well NS-5 Mishrif Formation-Nasriya Oil Field

2020 ◽  
Vol 10 (2) ◽  
pp. 17-35
Author(s):  
Hamzah Amer Abdulameer ◽  
Dr. Sameera Hamd-Allah
Keyword(s):  
Production Rate ◽  
Production Optimization ◽  
Oil Field ◽  
Reservoir Pressure ◽  
Pump Frequency ◽  
Individual Parameter ◽  
Well Production ◽  
Well Design ◽  
Natural Flow ◽  
Reservoir Conditions

As the reservoir conditions are in continuous changing during its life, well production rateand its performance will change and it needs to re-model according to the current situationsand to keep the production rate as high as possible.Well productivity is affected by changing in reservoir pressure, water cut, tubing size andwellhead pressure. For electrical submersible pump (ESP), it will also affected by numberof stages and operating frequency.In general, the production rate increases when reservoir pressure increases and/or water cutdecreases. Also the flow rate increase when tubing size increases and/or wellhead pressuredecreases. For ESP well, production rate increases when number of stages is increasedand/or pump frequency is increased.In this study, a nodal analysis software was used to design one well with natural flow andother with ESP. Reservoir, fluid and well information are taken from actual data of Mishrifformation-Nasriya oil field/ NS-5 well. Well design steps and data required in the modelwill be displayed and the optimization sensitivity keys will be applied on the model todetermine the effect of each individual parameter or when it combined with another one.

scholarly journals Analysis of Siphon String Application to Optimize Gas Lift Injection

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Sofani Muflih ◽  
Silvya Dewi Rahmawati
Keyword(s):  
Flow Regime ◽  
Production Rate ◽  
Flow Condition ◽  
Production Optimization ◽  
Font Size ◽  
Additional Advantage ◽  
Offshore Area ◽  
Well Model ◽  
Production Period ◽  
Gas Lift

<p><span style="font-size: small;"><span style="font-family: Times New Roman;"><em>B-</em><em>X</em><em> well is an oil producing well at Bravo field in Natuna offshore area, which was completed at IBS zone using 5-1/2 inch tubing size. </em><em>However, after several years of production period, the well’s production rate decreased due to reservoir depletion, and experienced gas lift performance problem indicated by unstable flowing condition (slugging flow). In year 2020, Siphon String installation is applied to the well in order to give deeper point of gas lift injection and better well’s production. The additional advantage by having smaller tubing size (insert tubing) is to reduce the slugging flow condition. The analysis of this siphon string installation at the B-X well, technically will be performed by evaluating gas lift performance and the flow regime inside the tubing using a Well Model simulator. The simulation was developed based on the real well condition. Several sensitivity analysis were done through several cases such as: variation in depth of gas lift point of injection, and the length of the siphon string. The simulation was required to evaluate the effectiveness of the existing installation, and to give better recommendation for the other well that has the same problem.  The result indicates that the depth of the current siphon string installation has been providing the optimum production rate, while the slugging flow condition will still be occurred at any given scenario of the siphon string depth due to the very low of well’s productivity. The similar procedure and evaluation can be implemented to other oil wells using gas lift injection located either in offshore or onshore field. </em></span></span></p><p><em><span style="font-family: Times New Roman; font-size: small;"> </span></em></p><p><em><span style="font-family: Times New Roman; font-size: small;">Keywords: Production Optimization, Siphon String, Flow Regime</span></em></p>

scholarly journals Optimizing Production Schedule of Coalbed Methane Wells Using a Stochastic Evolution Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Qiujia Hu ◽  
Xianmin Zhang ◽  
Xiang Wang ◽  
Bin Fan ◽  
Huimin Jia
Keyword(s):  
Production Rate ◽  
Coalbed Methane ◽  
Optimization Problem ◽  
Production Optimization ◽  
Production Performance ◽  
Production Schedule ◽  
Schedule Optimization ◽  
Well Production ◽  
Control Frequency ◽  
Optimized Schedule

Production optimization of coalbed methane (CBM) is a complex constrained nonlinear programming problem. Finding an optimal decision is challenging since the coal seams are generally heterogeneous with widespread cleats, fractures, and matrix pores, and the stress sensitivities are extremely strong; the production of CBM wells needs to be adjusted dynamically within a reasonable range to fit the complex physical dynamics of CBM reservoirs to maximize profits on a long-term horizon. To address these challenges, this paper focuses on the step-down production strategy, which reduces the bottom hole pressure (BHP) step by step to expand the pressure drop radius, mitigate the formation damage, and improve CBM recovery. The mathematical model of CBM well production schedule optimization problem is formulated. The objective of the optimization model is to maximize the cumulative gas production and the variables are chosen as BHP declines of every step. BHP and its decline rate constraints are also considered in the model. Since the optimization problem is high dimensional, nonlinear with many local minima and maxima, covariance matrix adaptation evolution strategy (CMA-ES), a stochastic, derivative-free intelligent algorithm, is selected. By integrating a reservoir simulator with CMA-ES, the optimization problem can be solved successfully. Experiments including both normal wells and real featured wells are studied. Results show that CMA-ES can converge to the optimal solution efficiently. With the increase of the number of variables, the converge rate decreases rapidly. CMA-ES needs 3 or even more times number of function evaluations to converge to 100% of the optimum value comparing to 99%. The optimized schedule can better fit the heterogeneity and complex dynamic changes of CBM reservoir, resulting a higher production rate peak and a higher stable period production rate. The cumulative production under the optimized schedule can increase by 20% or even more. Moreover, the effect of the control frequency on the production schedule optimization problem is investigated. With the increases of control frequency, the converge rate decreases rapidly and the production performance increases slightly, and the optimization algorithm has a higher risk of falling into local optima. The findings of this study can help to better understanding the relationship between control strategy and CBM well production performance and provide an effective tool to determine the optimal production schedule for CBM wells.

scholarly journals Production Rate Analysis of Fractured Horizontal Well considering Multitransport Mechanisms in Shale Gas Reservoir

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Qi-guo Liu ◽  
Wei-hong Wang ◽  
Hua Liu ◽  
Guangdong Zhang ◽  
Long-xin Li ◽  
...  
Keyword(s):  
Production Rate ◽  
Shale Gas ◽  
Horizontal Well ◽  
Production Performance ◽  
Natural Fractures ◽  
Gas Reservoir ◽  
Isothermal Adsorption ◽  
Well Production ◽  
Shale Gas Reservoir ◽  
Fractured Horizontal Well

Shale gas reservoir has been aggressively exploited around the world, which has complex pore structure with multiple transport mechanisms according to the reservoir characteristics. In this paper, a new comprehensive mathematical model is established to analyze the production performance of multiple fractured horizontal well (MFHW) in box-shaped shale gas reservoir considering multiscaled flow mechanisms (ad/desorption and Fick diffusion). In the model, the adsorbed gas is assumed not directly diffused into the natural macrofractures but into the macropores of matrix first and then flows into the natural fractures. The ad/desorption phenomenon of shale gas on the matrix particles is described by a combination of the Langmuir’s isothermal adsorption equation, continuity equation, gas state equation, and the motion equation in matrix system. On the basis of the Green’s function theory, the point source solution is derived under the assumption that gas flow from macropores into natural fractures follows transient interporosity and absorbed gas diffused into macropores from nanopores follows unsteady-state diffusion. The production rate expression of a MFHW producing at constant bottomhole pressure is obtained by using Duhamel’s principle. Moreover, the curves of well production rate and cumulative production vs. time are plotted by Stehfest numerical inversion algorithm and also the effects of influential factors on well production performance are analyzed. The results derived in this paper have significance to the guidance of shale gas reservoir development.

Experimental Study of the Fracture and Matrix Effects on Free-Fall Gravity Drainage With Micromodels

SPE Journal ◽  
2014 ◽  
Vol 20 (02) ◽  
pp. 324-336 ◽  
Author(s):  
Mehdi Bahari Moghaddam ◽  
Mohammad Reza Rasaei
Keyword(s):  
Production Rate ◽  
Oil Production ◽  
Free Fall ◽  
Gravity Drainage ◽  
Permeability Ratio ◽  
Fracture Spacing ◽  
Matrix Block ◽  
The Matrix ◽  
Fracture Opening ◽  
Single Matrix

Summary Free-fall gravity drainage (FFGD) is the main production mechanism in the gas-invaded zone of fractured reservoirs. The gravity and capillary forces are two major forces that control the production performance of a fractured system under an FFGD mechanism. Gravity force acts as a driving force to remove oil from the matrix block whereas the resistive capillary force tends to keep oil inside the matrix. In this study, a series of experiments was performed to study the effects of the geometrical characteristics of the fracture and matrix on the oil-production rate under an FFGD mechanism by use of a glass micromodel. The oil-recovery factor (RF) was also obtained for a single matrix block by use of different patterns. Results from the experiments show that different flow regimes occur during the production life of a single matrix block under a FFGD mechanism. The fluid flow is controlled by the capillary-dominated regime at the early stage and late time of production life, whereas it shows a stabilized bulk flow under a gravity-dominated regime is exhibited at other times. Experimental results revealed that for a narrow fracture opening, fracture capillary pressure has a form similar to that of the matrix block. Also, it was observed that the oil-production rate and RF of the matrix block decreased as the permeability ratio between two media (matrix block and fracture) increased. Lower production rate is achieved in larger-fracture-spacing micromodels. In addition, wider vertical fractures lead to an early breakthrough of gas in bottom horizontal fracture that makes up the main portion of oil traps in the matrix block, and this reduces the RF. Results from this study show that in a heterogeneous layered matrix block, both the drainage rate and RF decrease in comparison with a homogeneous matrix block. Finally, a multiple linear-regression analysis was performed to understand the dimensionless groups affecting the RF of the FFGD process. It was found that the Bond number cannot truly describe the process and other parameters such as the fracture-/matrix-permeability ratio; fracture spacing and fracture opening should also be considered.

Determination of Oil Well Production Rate by Analysis of the Real-Time Dynamometer Card

2016 ◽  
Author(s):  
Guoqing Han ◽  
Chaodong Tan ◽  
Jun Li ◽  
Zhejun Pan ◽  
He Zhang ◽  
...  
Keyword(s):  
Real Time ◽  
Production Rate ◽  
Oil Well ◽  
The Real ◽  
Well Production ◽  
Dynamometer Card

scholarly journals Two-dimensional numerical investigations on the termination of bilinear flow in fractures

2013 ◽  
Vol 5 (1) ◽  
pp. 391-425
Author(s):  
◽  
R. Jung ◽  
J. Renner
Keyword(s):  
Flow Field ◽  
Master Curve ◽  
Radial Flow ◽  
Dimensionless Time ◽  
Linear Flow ◽  
Type Curves ◽  
Straight Line ◽  
The Matrix ◽  
Line Characteristic ◽  
Fourth Root

Abstract. Bilinear flow occurs when fluid is drained from a permeable matrix by producing it through an enclosed fracture of finite conductivity intersecting a well along its axis. The terminology reflects the combination of two approximately linear flow regimes, one in the matrix with flow essentially perpendicular to the fracture and one along the fracture itself associated with the non-negligible pressure drop in it. We investigated the characteristics, in particular the termination, of bilinear flow by numerical modeling allowing an examination of the entire flow field without prescribing the flow geometry in the matrix. Fracture storage capacity was neglected relying on previous findings that bilinear flow is associated with a quasi-steady flow in the fracture. Numerical results were generalized by dimensionless presentation. Definition of a dimensionless time that other than in previous approaches does not use geometrical parameters of the fracture permitted identifying the dimensionless well pressure for the infinitely long fracture as the master curve for type curves of all fractures with finite length from the beginning of bilinear flow up to fully developed radial flow. In log-log-scale the master curve's logarithmic derivative initially follows a 1/4-slope-straight line (characteristic for bilinear flow) and gradually bends into a horizontal line (characteristic for radial flow) for long times. During the bilinear flow period, isobars normalized to well pressure propagate with fourth and second root of time in fracture and matrix, respectively. The width-to-length ratio of the pressure field increases proportional to the fourth root of time during the bilinear period and starts to deviate from this relation close to the deviation of well pressure and its derivative from their fourth-root-of-time relations. At this time, isobars are already significantly inclined with respect to the fracture. The type curves of finite fractures all deviate counterclockwise from the master curve instead of clockwise or counterclockwise from the 1/4-slope-straight line as previously proposed. The counterclockwise deviation from the master curve was identified as the arrival of a normalized isobar reflected at the fracture tip sixteen times earlier. Nevertheless, two distinct regimes were found regarding pressure at the fracture tip when bilinear flow ends. For dimensionless fracture conductivities TD < 1, a significant pressure increase is not observed at the fracture tip until bilinear flow is succeeded by radial flow at a fixed dimensionless time. For TD > 10, the pressure at the fracture tip has reached substantial fractions of the associated change in well pressure when the flow field transforms towards intermittent formation linear flow at times that scale inversely with the fourth power of dimensionless fracture conductivity. Our results suggest that semi-log plots of normalized well pressure provide a means for the determination of hydraulic parameters of fracture and matrix after shorter test duration than for conventional analysis.

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