Tight gas production model considering TPG as a function of pore pressure,permeability and water saturation

Threshold pressure gradient has great importance in efficient tight gas field development as well as for research and laboratory experiments.This experimental study is carried out to investigate the threshold pressure gradient in detail.Experiments are carried out with and without back pressure so that the effect of pore pressure on threshold pressure gradient may be observed.The trend of increasing or decreasing the threshold pressure gradient is totally opposite in the cases of considering and not considering the pore pressure.The results demonstrate that the pore pressure of tight gas reservoirs has great influence on threshold pressure gradient.The effects of other parameters like permeability and water saturation,in the presence of pore pressure,on threshold pressure gradient are also examined which show that the threshold pressure gradient increases with either a decrease in permeability or an increase in water saturation.Two new correlations of threshold pressure gradient on the basis of pore pressure and permeability,and pore pressure and water saturation,are also introduced.Based on these equations,new models for tight gas production are proposed.The gas slip correction factor is also considered during derivation of this proposed tight gas production models.Inflow performance relationship curves based on these proposed models show that production rates and absolute open flow potential are always be overestimated while ignoring the threshold pressure gradients.

Fast production and water-breakthrough analysis methods demonstrated using Volve Field data

When producing from conventional fields,the well rates are primarily constrained by the production-system in the early years of the field-life,while later in the field-life the production rates are primar-ily constrained by the reservoir deliverability.For the post-plateau production period,the reservoir deliverability will no longer potentially exceed the production-system well-rate constraints.Tradition-ally,analytical equations are used in a nodal analysis method that balances the pressure at the well inflow point from the reservoir(inflow performance relationship;IPR)with the pressure required for the vertical lift performance(VLP;or vertical flow performance;VFP)from the same point upward.A faster and simpler approach is proposed in the present study.Whereas,the classical IPR solutions are based on a constant well-rate solution of the diffusivity equation,use of a constant bottomhole pressure assumption can bypass the need for nodal analysis type pressure matching solutions to obtain the well rate.Instead,the well rate can be directly computed from the pressure decline in the reservoir and any production system capacity constraint can be imposed on the theoretical well rate due to the reservoir quality.The merits of the new approach are explained and illustrated by way of a detailed production analysis case study using open-access data from the Volve Field(Norwegian Continental Shelf).In addition,the case study of the Volve Field wells demonstrates a new water-breakthrough analysis method.