Crisman Annual Report 2009 - Harold Vance Department of ...

Experimental and Numerical Simulation Studies to Evaluate Improvement of Light
Oil Recovery by WACO 2
and SWACO 2
in Fractured Carbonate Reservoirs
Objectives
Oil recovery from mature fields deteriorates with
time and significant oil in place is then left behind.
Also, large economical hydrocarbon discoveries
have become rarer in recent years. Therefore, the
need to increase the reserves by improving recovery
techniques has become essential. Water alternating
gas (WAG) and simultaneous water and gas injection
(SWAG) have been proposed and applied with varying
results. However, extensive studies to examine
the latter have not been carried out, especially in
carbonate reservoirs and fractured rocks. Therefore,
this study will investigate the effect on oil recovery
and reservoir fluids by injecting water and CO 2
in
different modes.
This research project will study four injection
modes: waterflooding, continuous gas (CGI), water
alternating gas (WAG), and simultaneous water
and gas (SWAG). These modes will be injected in
two different sets of carbonate cores, fractured
and unfractured. The study aims to examine the
influence of these different modes of injection on
incremental light oil recovery and changes in rock
and fluid properties. Comparison parameters would
be as follows:
» Oil recovery versus time
» Residual oil saturation in the core matrix and the
fracture using X-Ray CT scanning
» Displacement efficiency improvement by the
addition of NaI to the injected water
Approach
This research uses a core flood apparatus which
contains high-grade aluminum to allow for X-Ray
CT scanning. The core is connected to a 40-ft
slimtube coil that will provide the necessary length
to achieve miscibility, Figs. 1 and 2. The carbonate
core measures 6 in long by 2 in OD on which the
two scenarios will be investigated. The fracture will
be created by sawing the core and placing a 1 mm
spacer in the fracture to keep it open, and putting
the fractured core in the coreflood cell. Injection
pressures will be at 1900 psi to simulate downhole
conditions and ensure miscibility between injectant
gases and oil in place. Numerical simulation (CMG)
will be conducted to model the experimental results.
Accomplishments
A fit-to-purpose experimental apparatus was
designed. The minimum miscibility pressure (MMP)
between west Texas light oil and CO 2
has been
measured using the industry standard method,
slimtube, and numerical simulation. It was found
that the core will not permit multiple contact
miscibility to occur as tested by the slimtube. This is
because of the core’s short length and heterogeneity
CRISMAN INSTITUTE
Project Information
1.7.3 Analytical Modeling and Experimental Studies
to Evaluate Improvement and Recovery of Light Oil in
Carbonate Reservoirs by Simultaneous Water Alternating
Gas (SWAG)
Related Publications
Mamora, D.D.. and Seo, J. G. Enhanced Gas Recovery by
Carbon Dioxide Sequestration in Depleted Gas Reservoirs.
Paper 77347, presented at the 2002 SPE-ATCE, San
Antonio, Texas, 29 September – 2 October.
Silva, Carlos F. R.: 2003. Water Alternating Enriched Gas
Injection to Enhance Oil Production and Recovery from
San Francisco Field, Colombia. MS thesis, Texas A&M U.,
College Station, Texas.
Contacts
Daulat Mamora
979.845.2962
daulat.mamora@pe.tamu.edu
Fig. 1. Coreholer connected to slimtube.
Ahmed Aleidan
44
Crisman Annual Report 2009