Waterflooding Optimization Through A Better Understanding Of Production Allocation

Abstract

Production allocation is the process of understanding from which horizons perforated in an
oil well the production came from. This allows for material balance calculations to determine
how much the different levels have produced of the different phases and where the remaining
oil is located. It is an essential process in optimizing a water floods. In many studies carried
out in the past, analytical techniques (such as decline curve analyses) have been very
successful in identifying infill drilling potentials and workovers. However as the fields have
become more mature a finer understanding of where the production came from has been
required. Attempts have been made using horizon productivities combined with production
logging to derive a better allocation of the production by sands. However as the level of
water injection varies from sand to sand productivity or kh is a poor allocation technique.
A method is presented here to do the production allocation based on a 3D property model
using streamline simulation. The streamline simulation allows for a study of a model with
numerous cells. This model will take into account the injection production on a sand by sand
level according to historic information. The model was matched primarily on liquid
production and allocation factors for oil and water were generated for each of the sands and
every month of the production history. The offset in the production match was adjusted by
using the calibration factors in combination with the actual historical well performance. The
outcome was a process that in 4 weeks would create a sand by sand production allocation for
more than 100 wells, 13 sands and more than 20 years of production history. In addition for
every injector it was possible to identify which producers were supported according to the
property model. In addition the approach can be used to assess the uncertainty of the
allocation given more geostatistical realizations and approximate water cut matches. Once
the process is complete, the standard analytical processes can be run on a finer sand level.
The value of the approach is the speed and the ability to link the production allocation to the
reservoir characterization.