New Approach For The Performance of Reservoirs Depleted by Long Horizontal Wellbores With Closed Sections

Abstract

This paper introduces a new approach for reservoir performance where long 
horizontal wellbores are extended in the porous media with the existence of 
closed sections. It focuses on the impact of these sections on the pressure 
behavior, flow regimes, and productivity index considering different 
characteristics for the closed sections in terms of the length and petrophysical 
properties. New analytical solutions for the flow equations are presented wherein 
three porous media are considered in the rectangular closed reservoirs of 
different configurations. The methodology used in this approach includes 
different tasks. The first is developing analytical models for the pressure drop 
caused by the production at a constant sandface flow rate from a horizontal 
wellbore where a part of it is closed. These models are developed based on the 
fact that the porous media with the existence of the closed sections in the 
horizontal wellbores consists of three regions. The first represents the porous 
media in the vicinity of the open section of the wellbore and extends to a 
distance equal to half the formation thickness while the second is the porous 
media of the open section that extends beyond the first region and reaches the 
reservoir boundary. The third region represents the porous media of the closed 
sections that extend from the wellbore to the reservoir boundary. In the second 
task, the proposed models are solved for different reservoir configurations, 
wellbore lengths, and closed and open section characteristics. The impact of 
closed sections on transient and stabilized pseudo-steady state productivity 
indices are demonstrated in third tacks while the analytical models of the 
observed flow regimes in the porous media are presented in the fourth task with 
a major focus given to those impacted by the closed sections. The results of the 
developed models are verified by the comparison with the results obtained from 
the available well-known models in the literature. The outcomes of this study can 
be summarized in the following points: 1) The pressure behavior, flow regimes, 
and productivity index are significantly influenced by the existence of closed 
sections. This influence is significant during early production time, but it 
decreases during intermediate production, however, it is not seen at late 
production time. 2) The impact of closed sections becomes more severe when the 
petrophysical properties of the closed sections are greatly different from those of 
open sections. 3) The pressure behavior of early production time is not affected 
by the petrophysical properties of the closed section porous media while pseudo
steady state flow is significantly impacted by these properties. 4) The pressure 
and pressure derivative behaviors of long horizontal wellbores with long closed 
sections are similar to those developed in reservoirs depleted by hydraulic there is a great difference in the petrophysical properties between closed and 
open sections, however, the length of the closed sections may not have such 
impact.   Two novel points are reached in this study. The first is developing new 
analytical models for the pressure behavior of reservoirs depleted by horizontal 
wellbores with closed sections. The second is observing a new bi-linear flow 
regime instead of linear flow regime. This flow regime represents simultaneous 
linear flow from the closed section porous media to the open section and from 
the open section to the porous media in the vicinity of the open section of the 
wellbore. New analytical models for the pressure and pressure derivative of this 
flow regime is introduced in this study.