In coalbed methane (CBM) reservoirs, permeability changes dynamically throughout the life of the reservoir as the pressure depletes due to production. The dynamic variation of coal permeability mainly depends on the combined effect of effective stresses and coal matrix shrinkage caused by gas desorption. Under the conditions of pressure-dependent diffusivity in coal reservoirs, the flow mechanism in CBM reservoirs complicates the solution of the two-phase diffusivity equation. In this study, the authors present a new approach to describe the CBM reservoir diffusivity equation in a form that fully couples the pressure-dependent diffusivity and time-dependent desorption effects in the transport mechanism of CBM reservoirs. This paper presents a semi-analytical solution of the fully coupled diffusivity equation under pseudo-steady state flow conditions. The proposed solution is then leveraged to predict the performance of a two-phase CBM well using an approach that is alternative to the conventional method for CBM reservoirs. The proposed semi-analytical model presents a computational method not only to predict the performance but also to evaluate the performance of a producing CBM well. The model presented in this study has been used to investigate the impact of pressure-dependent diffusivity and time-dependent desorption on the production behavior of CBM wells producing under pseudo-steady state conditions. The results of the semi-analytical solution have been verified using numerical simulator CMG-GEM as well as actual in-field data.

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Background: Acute viral hepatitis (AVH) is one of the common infections in developing nation. Hepatotrophic virus causes AVH and most of the time it has self-limiting course. HAV is most common cause of AVH. Suboptimal dietary cultural practices are common in our nation. This study was done to know the impact of suboptimal dietary practices done in AVH.Methods: Observational study conducted with 50 children with AVH. Dietary assessment was done at three point of time.  First During AVH, second, pre illness and then two weeks after nutritional counselling. Data of dietary modification done by parents/caregiver during AVH recorded. History of herbal medicine taken for treatment of AVH enquired.Results: HAV positive was (72%), HEV positivity was in 8 (16%) cases, hepatitis B was positive in 4 (8%) children and dual infection HAV+HEV was detected in 2 (4%) children. Many parents did dietary modification due to AVH and also by some local treating physicians, 18 (36%) patients were also on herbal medication for treatment of AVH. During AVH the mean calorie and protein requirement decreased from 96% to 54% and 92% to 43% respectively. Two weeks after nutritional counseling the mean calorie and protein intake increased from 54% to 88% and 43% to 84% respectively. This change in calorie and protein was statistically significant (p<0.01) Non-vegetarian diet preference was restarted in many of them after nutritional counseling.Conclusions: This observational study revealed that suboptimal dietary cultural practices are prevalent in India. Majority of children were on bland diet and receiving inadequate proteins and calories.