Summary
Production enhancement and ultimate recovery improvement have given
horizontal wells the edge over vertical wells in many marginal reservoirs.
However, it is more expensive to drill and complete a horizontal well than a
vertical one. Therefore, to determine the economical feasibility of drilling a
horizontal well, engineers need reliable methods to estimate its
productivity.
After a broad literature review, a simple semianalytical model has been
developed in this study for predicting the productivity of horizontal oil
wells. This model couples flow from a box-shaped drainage volume to flow in the
wellbore. Along with friction, acceleration, and fluid-inflow effect, change in
flow regime from laminar to turbulent is also taken into account to describe
flow in the wellbore. The reservoir-inflow model used in this productivity
model represents flow in the reservoir using a combination of 1D and 2D models
and also considers varying skin along the wellbore to account for the
heterogeneity of the near-wellbore region because of drilling-fluid invasion
into the formation. In addition, reservoir-permeability anisotropy and
convergence of flow to the wellbore have been taken into account in this inflow
model. Comparison of this model with three existing models using field data
reveals that the proposed model is more accurate because of more-realistic
modeling of reservoir inflow and wellbore flow.
The semianalytical nature of this coupling model makes it comprehensive and
applicable to reservoirs with varying conditions, especially heterogeneous
reservoirs. Moreover, this productivity model can be extended easily to
estimate the deliverability of multilateral wells by coupling the inflow
performance of individual laterals with hydraulics in buildup sections and the
main vertical section. A logical procedure for calculating the deliverability
of multilateral wells by using this productivity model is described in this
paper.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
15 October 2009
- Meeting paper published:
8 December 2009
- Revised manuscript received:
15 April 2010
- Manuscript approved:
7 July 2010
- Published online:
7 October 2010
- Version of record:
23 February 2011
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