Peak Gas Production Research Articles

Influence of horizontal well section length on the depressurization development effect of natural gas hydrate reservoirs

The second production test of natural gas hydrate (referred to as hydrate) reservoir in the Shenhu sea area of the northern South China Sea shows that horizontal wells have greater potential than vertical wells in the depressurization production of hydrate reservoirs, but the length of horizontal section to achieve remarkable development effect has not been determined. To this end, a set of production simulation experiment device was independently designed. After the influences of horizontal well section length on gas and water production behaviors and temperature and pressure change laws during the depressurization development of hydrate reservoirs were studied by means of physical experiment, an equal-scale numerical simulation model was established by numerical simulation method. And based on history matching, the change laws of hydrate saturation and gas saturation were analyzed. And the following conclusions were reached. First, for the hydrate reservoirs where water and hydrate coexist, a great amount of high-pressure movable water is produced in the early stage of depressurization development while the formation pressure drops quickly and hydrates are mostly dissociated. In the later stage of depressurization development, there is no stable heat supply. Therefore, the gas production rate presents a trend of fast rise to the peak in the early stage and then concussive decline. Second, horizontal well can effectively increase the water and gas drainage areas, so the longer the horizontal well section is, the higher the peak gas production rate and cumulative gas production are and the shorter time it takes to reach the peak gas production rate, but the faster the gas production decline is in the case of no heat supply. Third, an obvious low hydrate saturation area is formed near the horizontal well, so a long horizontal section is helpful to enlarge the hydrate dissociation area, but in the later stage of depressurization development, there are still a lot of undissociated hydrates in hydrate reservoirs, so the development mode shall be modified to further promote the dissociation of hydrates. Fourth, due to the heat transfer of cap rocks and the gas/water gravity difference, a secondary gas cap is formed easily in the process of depressurization development, so if the horizontal well is drilled near the upper part of a hydrate reservoir, the overlay of dissociated gas can be alleviated, and consequently the production and development effect of dissociated gas are improved.

Simulation of gas transport in a landfill with layered new and old municipal solid waste

Average biodegradation rate of newly filled municipal solid waste (MSW) in landfills is relatively fast, and the landfill gas produced by the new MSW biodegradation can cause great variations in gas pressure. To predict the gas pressure distribution in the MSW layer, a one-dimensional gas transport model is established in this study. The following factors are considered in this model: (1) the variation of gas permeability with depth; (2) the anisotropy ratio of gas permeability; (3) the settlement caused by waste biodegradation. Furthermore, a single peak model for gas production is applied as the source term of gas production. The equation for settlement caused by waste biodegradation is presented, and the time of peak gas production rate is obtained by fitting the settlement of the newly filled layer. The stratification of the unsaturated and saturated regions is taken into account by distinguishing the difference in gas saturation. The layering of the new and old waste layers is considered by distinguishing the difference in the length of time that waste has been degraded to produce gas. Based on the method of numerical calculation, the gas pressure distribution in the landfill with layered new and old MSW is well simulated. The position where the maximum gas pressure occurs is found. The sensitivity analysis shows that the influence of the anisotropy ratio on gas pressure distribution is more significant.

Experimental study on gas mass transfer process in a heterogeneous coal reservoir

Series and parallel seepage simulation experiments of coal matrix pore sample, natural fracture sample and artificial fracture sample with three permeability ranges were designed and performed. These three samples represent the low permeability zone, transition zone and fracturing zone in the development coal seam. In the parallel experiment, fracturing fractures are the dominant seepage channel, and the gas seepage in the matrix and natural fractures is limited. In the series experiment, a high-efficiency mass transfer stage has the displacement pressure difference is greater than 7.3 MPa, which represents the coal reservoir has a strong gas supply capacity. On the contrary, a low-efficiency mass transfer stage appears when the displacement pressure difference is less than 7.3 MPa, suggesting the decline in gas supply capacity. Due to the rapid output of near-well desorbed gas, a short gas production peak will be formed in the early production stage. After that, due to insufficient gas supply on the parallel path, the gas production rate drops rapidly. The second gas production peak appears in the high-efficiency mass transfer stage. Finally, due to the limited expansion of the pressure drop funnel, the gas production gradually decreased and eventually stabilized after entering the low-efficiency mass transfer stage.

E&P Notes (February 2021)

E&P Notes (February 2021)

Enhancing Methane Yield in Dry Anaerobic Digestion from Municipal Solid Waste Through the Intermittent and Low-Strength Ultrasonic Technology

One of the most challenging issues for dry anaerobic digestion (AD) is its limited mass transfer due to low water content; however, the mass transfer can be enhanced by the ultrasonic waves. In this research, a set of ultrasonic technology experiments are evaluated before or during dry AD to enhance methane yield. In the pretreatment stage, ultrasonic could promote the hydrolysis of organic substances. The sCOD concentration was increased by 4 %, and the cumulative methane production was 196.5 mL/g.VS, which was increased by 32 %. Moreover, during the dry AD reaction process, through the intermittent and low-strength ultrasonic technology, the optimal cumulative methane production was 230.65 mL/g.VS, which was increased by 56%; the maximum daily methane production rate was 38.46 mL/g.VS, which was increased by 77.17 %. The lag period of dry AD was shortened, and the gas production peak was advanced. The dominant microbial communities in dry AD system are analyzed. This research will provide suggestions for the application of dry AD technology to MSW treatment.

Effect of micro-oxygen pretreatment on gas production characteristics of anaerobic digestion of kitchen waste

Micro-oxygen pretreatment of kitchen waste was done to improve the gas production efficiency of anaerobic fermentation and shorten the fermentation cycle of kitchen waste. The results demonstrated that with an oxygen supply of 20 mL, the peak gas production increased from 498 to 601 mL, and the theoretical gas production increased by 4.5 mL/g VS (volatiles solid) compared with those of the control group R1–R4. The anaerobic fermentation entered the late stage on day 25, which was 13 days earlier than that of the control group. The chemical oxygen demand and ammonia nitrogen contents in the treatment groups of R1–R4 were relatively stable. An oxygen supply of 20 mL was conducive to stimulating the facultative anaerobes, promoting the decomposition of nitrogenous compounds and organic matter, and improving the anaerobic fermentation efficiency. A lesser amount of oxygen (≤ 15 mL) was unable to effectively improve the gas production efficiency of anaerobic fermentation, although it exerted a certain inhibitory effect on anaerobic fermentation.

The effects of cross-formational water flow on production in coal seam gas reservoir: A case study of Qinshui Basin in China

In coal seam gas (CSG) reservoirs, hydraulic connectivity usually exists between the coal and overlying permeable formation, which results in the delay of the dewatering process and a large volume of produced water. The cross-formational water flow can dramatically influence the production of CSG reservoirs, reduce the economic viability of production and increase the impact on the environment.To assess the cross-formational water flow of a CSG well, this study investigates the effects of cross-formational water flow from the overlying permeable formation on gas production. Simulation models are constructed to represent the water crossflow in four connection scenarios, including contact zone with and without penetrated fracture, and no-contact zone with and without penetrated fracture. The penetration ratio, defined as the ratio of fracture height in permeable formation to the formation thickness, is employed to characterize the extension degree of hydraulic fracture in the overlying formation. The effects of cross-formational water flow on CSG production are analyzed using dimensionless production curves and relative permeability curves calculated from the production history. The field application of this study is demonstrated by the production history of fractured CSG wells in the Qinshui Basin, China.The simulation results show that if the overlying formation is directly connected to the coal seam (contact zone scenario), the hydraulic fracture leads to the decrease of the peak gas production rate with the cumulative water production increasing dramatically. If the overlying formation is connected to the coal seam by hydraulic fractures only (no-contact zone scenario), gas production increases in two stages. Initially, the gas production rate exhibits a slow increase, followed by a fast increase before reaching the peak rate. When the hydraulic fracture penetrates the overlying formation, a 10% increase of the penetration ratio results in 0.55% and 1.82% increase of cumulative water production in the indirect and direct connection scenarios, respectively. In both scenarios, 10% penetration ratio increase leads to 7.41% reduction of gas production rate. The methods and simulation results presented in this work can be used to evaluate the impacts of cross-formational water flow on gas production and identify the cross-formational water flow in CSG wells from production history.

In vitro digestion characteristics of various combinations of elephant grass hay, gliricidia hay or silage, soybean meal and corn meal in rations for sheep

This study examined fermentation rates and kinetics of sheep rations based on combinations of elephant grass hay, gliricidia (Gliricidia sepium) hay or silage, soybean meal and corn meal using in vitro techniques. Three rations were prepared, namely: Control (elephant grass hay + soybean meal + corn meal); gliricidia hay (elephant grass hay + soybean meal + corn meal + gliricidia hay); and gliricidia silage (elephant grass hay + soybean meal + corn meal + gliricidia silage). A fixed ratio of roughage:concentrate of 55:45 was maintained for all rations, which were isocaloric and designed to support sheep gains of 200 g/day. The gliricidia replaced 57.6% of the soybean meal in the rations containing gliricidia and 81.8% of the elephant grass hay. Fermentation rates and kinetics, in vitro dry matter digestibility (IVDMD) and degradability of the rations were evaluated. Rations containing gliricidia as both hay and silage had higher (P<0.05) IVDMD than the Control ration (67.8 and 66.2 vs. 59.8%). The degradability of the ration containing gliricidia hay was higher (P<0.05) than that of the gliricidia silage ration (57.8 vs. 50.5%), whereas the Control showed an intermediate value (54.4%). The ration containing gliricidia hay and the Control produced more gas in the first 24 h than the ration containing gliricidia silage, and the gliricidia hay ration showed the shortest colonization time. Peak gas production occurred for the ration with gliricidia silage later than for the other rations. The study showed that substituting soybean meal with preserved gliricidia can result in higher digestibility of sheep rations. Feeding studies with animals are now warranted to verify these laboratory findings.

Development of Shale Gas Prediction Models for Long-Term Production and Economics Based on Early Production Data in Barnett Reservoir

This study examined the relationship between the early production data and the long-term performance of shale gas wells, including the estimated ultimate recovery (EUR) and economics. The investigated early production data are peak gas production rate, 3-, 6-, 12-, 18-, and 24-month cumulative gas production (CGP). Based on production data analysis of 485 reservoir simulation datasets, CGP at 12 months (CGP_12m) was selected as a key input parameter to predict a long-term shale gas well’s performance in terms of the EUR and net present value (NPV) for a given well. The developed prediction models were then validated using the field production data from 164 wells which have more than 10 years of production history in Barnett Shale, USA. The validation results showed strong correlations between the predicted data and field data. This suggests that the proposed models can predict the shale gas production and economics reliably in Barnett shale area. Only a short history of production (one year) can be used to estimate the EUR and NPV of various production periods for a gas well. Moreover, the proposed prediction models are consistently applied for young wells with short production histories and lack of reservoir and hydraulic fracturing data.

Effect of Zn Addition on the Cd-Containing Anaerobic Fermentation Process: Biodegradation and Microbial Communities.

Anaerobic fermentation is considered as a cost-effective way of biomass waste disposal. However, the compound heavy metals contained in the biomass may induce complex effects on anaerobic fermentation, which limit the utilization of metal-contaminated biowaste. In this study, the impacts of Cd and Zn addition on biogas properties, process stability, substrate biodegradation, enzyme activity, and microbial properties were studied. The results showed that the addition of Cd together with Zn (Cd+Zn) increased the maximum daily and cumulative biogas yields, and brought forward the gas production peak compared with the Cd-added group. Taking the whole fermentation process into account, the promotion effects of adding Zn into the Cd-containing fermentation system on biogas yields were mainly attributable to better process stability, higher average NH4+-N concentration in the later stage of fermentation, reduced COD (p < 0.05), and increased biodegradability of lignocelluloses (p < 0.01), especially cellulose (p < 0.05) and lignin (p < 0.01). Meanwhile, the addition of Zn promoted the coenzyme M activity (p < 0.05), and increased the absolute abundance of Methanothermobacter. The bacteria communities during the fermentation process were responsible for the degradation of lignocelluloses. The results demonstrated that the addition of appropriate Zn into the Cd-containing fermentation system enhanced the efficiency of anaerobic fermentation and utilization of biowaste.

Influence of depressurization rate on gas production capacity of high-rank coal in the south of Qinshui Basin, China

Abstract A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.

LIQUID HOLDUP MANAGEMENT BY PREDICTING STEADY STATE TURNDOWN RATE IN WET GAS PIPELINE NETWORK

Now days, one of the greatest challenges in gas development is transport the fluid especially multiphase fluid to long distances and multiphase pipeline to sell point. Yet, a challenge to transport multiphase fluid is how to operate the systemsin operating a long distance, large diameter, and multiphase pipeline.The operating system include how to manage high liquid holdup, mainly built during low production rate (turn down rate) periods especially during transient operations such as restart and ramp-up, so that liquid surge arriving onshore will not exceed the liquid handling capacity of the slug catcher. The objective of this research is to predict liquid trapped in pipeline network by analysis turn down rate in order to determine minimal gas production rate for stable operation. This research was carried out by two steps: Simulation Approach and Optimization Techniques. Simulation approach include define fluid composition and built pipeline network configuration while optimization technique include conduct scenario for turn down rate. The fluid composition from wellhead to manifold is wet gas. First scenario and Second scenario of turndown rate yield minimum gas rate for stable operation. The pipeline has to be operated above 600 MMSCFD from peak gas production rate is 1200 MMSCFD (A-Manifold Mainline) and 60 MMSCFD from peak gas production rate is 150 MMSCFD for D-Manifold Mainline.

Dietary Fructan Intolerance Another Jigsaw in Irritable Bowel Syndrome (IBS) Puzzle

Introduction: Fructan are polymerized fructo-oligosaccharides that are present in wheat, onion, garlic, artichoke and other common foods, with an estimated daily intake of 1-20 g in USA. Fructans are believed to be completely malabsorbed but we found that 33% of healthy humans do not show malabsorption. Fructan maldigestion may cause symptoms and intolerance in patients with IBS. We aimed (1) To assess the feasibility of fructan breath test (FrBT), (2) To investigate whether dietary fructan intolerance causes IBS.Figure: Proportion of the patient who has positive Fructan Breath Test.Figure. 2: Correlation of Symptoms & Fructan Breath Test, n=102.Methods: Patients with IBS (Rome III), negative GI evaluations (endoscopy and CT), and negative glucose breath tests were evaluated. After an overnight fast, subjects ingested 10 g of fructan dissolved in 100 cc water. H2 and CH4 samples were collected at baseline and every 30 minutes for 3 hours. A change ≥ 20 ppm over baseline H2 or ≥ 15 ppm over baseline CH4 values were considered positive. AUCs and time to peak gas production were calculated. Symptoms were assessed at baseline and during the FrBT. IBS symptom reproduction, abdominal pain, cramping, bloating, fullness, nausea, indigestion, diarrhea, gas, distention was recorded using a likert scale of 0-3. Symptom scores were compared between negative test group and intolerance. Results: 102 patients (f/m=73/29, mean age 50 years) were evaluated. Positive FrBT were found in 65 (64%), and 52(51%) had reproduction of their IBS symptoms. Negative FrBT were found in 37 (36%), and 17(16%) had reproduction of their IBS symptoms. The mean peak rise in H2 was 69ppm, and mean time to reach peak of 2.1 hours, and the mean H2 AUC was 92ppm-hours. In patients with positive test, the peak rise in CH4 was 25ppm, the time to reach peak was 2.1 hours, and CH4 AUC was 46.3ppm-hours. Significantly greater number of patients with positive FrBT showed IBS symptom reproduction during test (52 vs 17, P < 0.05) than those with negative test (mean 26.8 versus 31.8, P=0.49). Overall symptom score was similar between groups (mean 26.8 vs 31.8, P=0.49). Conclusion: In a selected group of patients with IBS, approximately 64% had fructan malabsorption and 51% had fructan intolerance. The dictum that dietary fructan are always malabsorbed in humans seems incorrect. Symptoms appear to be poor predictors of a positive or negative test. FrBT is safe, practical, and useful test. It could help to identify a subgroup of IBS patients that may benefit from a targeted trial of low fructan diet, rather than FODMAP restricted diet.

Numerical analysis of depressurization production of natural gas hydrate from different lithology oceanic reservoirs with isotropic and anisotropic permeability

Natural gas hydrate (NGH) is a promising alternative energy and mainly distributes in deep oceanic sediments. The intrinsic permeability of hydrate-bearing layers can potentially influence heat and pressure transfer during depressurization-induced NGH dissociation. By taking siltstone, sand and clay reservoirs in Shenhu area of South China Sea as examples, this study numerically investigates the effects of the magnitude and anisotropy of reservoir permeability on NGH production process and main physical field evolution. Results reveal that permeability anisotropy could impede advective interaction of fluids in vertical direction, significantly changing temperature and pressure evolution during NGH dissociation. Consequently, NGH dissociation slows down, delaying the coming of peak gas production rate. Some degrees of permeability anisotropy even lead to much earlier termination of NGH dissociation. In this case, the more permeable sand reservoir could possibly have a lower gas production potential than the less permeable siltstone and clay reservoirs. The permeable overburden limits the fluid pressure reduction and weakens the efforts of depressurization production. The re-production by further lowering well pressure only lasts for a short time. Comparatively, the depressurization of constant production mass rate is more effective but only provides a small contribution for the total gas yield.

Developing synthetic reservoir type curve model for use in evaluating surface facility and gathering pipe network designs

Surface facilities and unconventional gas gathering networks are typically designed to collect gas from a large number of wells to a central location. The unit operations that make up the surface network need to be installed before the wells are producing and thus need to be sized on predicted performance rather than actual performance which is not known until production data is available. This means each reservoir's production profile which is based on uncertain input parameters and imperfect reservoir models forms the sizing basis for the surface facilities.In this study a method is developed to generate synthetic reservoir flow type curves based on a set of input parameters that is independent of reservoir parameters. The main qualitative characteristics of an unconventional gas reservoir type curve are described such as gas ramp to peak, peak gas flow and production decline, along with the discontinuities and variations from expected performance seen in operating trends. The synthetic type curve proposed in this work can be parameterised to mimic these characteristics, along with a well deliverability mechanism and subsurface communication between wells.The method of being able to describe a type curve by means of input parameterisation allows an unconventional gas surface facility of gathering pipe network and in-field booster compressors to be designed against many sets of synthetic type curves rapidly generated by randomisation of those input parameters.

Impact of water blocking in fractures on the performance of hydraulically fractured horizontal wells in tight gas reservoir

Tight gas is a major gas resource which accounts for 14% of the total gas resources and 29% of unconventional gas in the world. The natural production of tight reservoir is very low, and multi-stage fracturing technology is widely used in horizontal wells. Multi-stage hydraulic fracturing for stimulating tight gas reservoirs requires a significant amount of fracturing fluid, which is usually water-based. Water blocking is considered as a potential type of damage in tight gas reservoirs. There are many factors affecting the production decline caused by the water blocking in fractures. However, the water blocking and fluid segregation in fractures are ignored. This study investigates the characteristics of water blocking in fractures and the effects of wettability, fracture fluid viscosity and fracture fluid filtration on water blocking and gas production. Numerical simulation is used to show that three stages can be used to describe the change of water saturation at the top and bottom of fractures, where the second stage indicates water blocking in hydraulic fractures. The results demonstrate that the stronger the interfacial tension, the more obvious the water wettability is, and the more water traps in the reservoir matrix. Decreasing interfacial tension improves the load recovery, and reduces the formation damage, and further enhances the gas production. A higher fracturing fluid viscosity causes more water traps at the bottom of fractures and intensifies the formation damage on tight gas wells. Results indicate that the fracturing fluid filtration has a great impact on the flowback performance and later gas production. Results suggest that increasing the filter cake thickness decreases the gas production peak value, and delays the time showing the peak of gas production, and further reduces the cumulative gas production.

Effect of ferrous chloride on biogas production and enzymatic activities during anaerobic fermentation of cow dung and Phragmites straw

The effect of ferrous (added as FeCl2) on the anaerobic co-digestion of Phragmites straw and cow dung was studied by investigating the biogas properties, pH values, organic matter degradation (COD) and enzyme activities (cellulase, protease and dehydrogenase) at different stages of mesophilic fermentation. The results showed that Fe(2+) addition increased the cumulative biogas yields by 18.1% by extending the peak period with high daily biogas yields. Meanwhile, the methane (CH4) contents in the Fe(2+) added groups were generally higher than the control group before the 15th day. The pH values were not significantly impacted by Fe(2+) concentrations during the fermentation process. The COD concentrations, cellulase, protease and dehydrogenase activities varied with the added Fe(2+) concentrations and the stages of the fermentation process. At the beginning stage of fermentation (4th day), Fe(2+) addition increased the biogas production by improving the cellulase and dehydrogenase activities which caused a decline in COD. At the peak stage of fermentation (8th day), Fe(2+) addition enhanced the cellulase and protease activities, and resulted in lower COD contents than the control group. When the biogas yields decreased again (13th day), the COD contents varied similar with the protease and dehydrogenase activities, whilst cellulase activities were not sensitive to Fe(2+) concentrations. At the end of fermentation (26th day), Fe(2+) addition decreased the cellulase activities, led to lower COD contents and finally resulted the lower biogas yields than the control group. Taking the whole fermentation process into account, the promoting effect of Fe(2+) addition on biogas yields was mainly attributed to the extension of the gas production peak stage and the improvement of cellulase activities.

Preliminary numerical modelling of CO2 gas foaming in heavy oil and simulations of oil production from heavy oil reservoirs

Basic understanding of numerical modelling for the effects of CO2 foaming on heavy oil production behaviour using the huff‐and‐puff process is relevant for CO2‐EOR performance. The numerical model was constructed based on laboratory measurements: CO2 solubility, foam swelling, and apparent viscosity. The model for unsaturated solubility in porous media, such as sandstone cores and oil reservoirs, was proposed by defining CO2 solubility in heavy oil for generating foamy oil. The foaming process was modelled with four kinds of foamy oils at discrete depressurizations below each equilibrium pressure. A numerical model of apparent foam viscosity with discrete depressurization was set up based on experimental measurements as a function of pressures and temperatures of 0.1–10 MPa and 20–50 °C. The matching between the numerical simulations of heavy oil drainage and experimental measurements of foaming in Berea sandstone cores (Psat = 10 MPa at 50 °C) shows 31 % oil recovery after depressurization to atmospheric pressure. The numerical simulation results of heavy oil production at field‐scale showed that CO2 gas production quickly increases after depressurization and then the foamy oil production increases following the peak gas production rate. In the first cycle of the huff‐and‐puff process, the maximum oil production rate ranged from 4–68 m3/day. From the sensitivity study it can be concluded that the initial oil saturation and the CO2 dissolution zone as compared with reservoir size play a main function in heavy oil production by CO2 gas foaming in the huff‐and‐puff process.

Gas Production from Offshore Methane Hydrate Layer and Seabed Subsidence by Depressurization Method

Numerical simulations on consolidation effects have been carried out for gas production from offshore methane hydrates (MH) layers and subsidence at seafloor. MH dissociation is affected by not only MH equilibrium line but also consolidation (mechanical compaction) depended on depressurization in the MH reservoir. Firstly, to confirm present model on consolidation with effective stress, the history matching on gas production and consolidation has been done to the experimental results using with synthetic sand MH core presented by Sakamoto et al. (2009). In addition, the comparisons of numerical simulation results of present and Kurihara et al. (2009) were carried out to check applicability of present models for gas production from MH reservoir in field scale by depressurization method. The delays of pressure propagation in the MH reservoir and elapsed time at peak gas production rate were predicted by considering consolidation effects by depressurization method. Finally, seabed subsidence during gas production from MH reservoirs was numerically simulated. The maximum seabed subsidence has been predicted to be roughly 0.5 to 2 m after 50 days of gas production from MH reservoirs that elastic modulus is 400 to 100 MPa at MH saturation = 0.

Peak Gas Production Analysis and Influencing Factors Study of Coal Bed Methane Well

The value of peak gas production and the time when it reaches are two important marks for coal bed methane (CBM) well’s gas production curve. This paper takes M CBM gas field of A country’s B basin as actual production instance. Firstly, based on the CBM producing mechanism, the existence reason of peak gas rate is analyzed; secondly, the influencing factors of the value of peak gas production and the time when it reaches is studied by numerical simulation method. And sensitivity order of the influencing factors is obtained. The study results indicate that: the value of peak gas production has positive correlation with properties: permeability, gas content, coal bed net pay and gas saturation; while negative correlation with desorption time and cleat porosity. And the strong to weak intensity of sensitivity is permeability, gas content, desorption time, net coal bed pay, cleat porosity, gas saturation. The time when peak gas production reaches is markedly influenced by the value desorption time and cleat porosity, the smaller of the two parameters, the shorter of the time when peak gas production reaches.