(186n) Optimization of Single-Well CO2 Injection for Enhancement of Tight Oil Production

Optimization
of single-well CO₂ injection for enhancement of tight oil production

CO₂
injection is a common approach to enhance recovery in conventional reservoirs,
but recent efforts to apply this technique in tight oil wells have shown limited
incremental oil recovery.  A novel idea
to address the problem employs a single horizontal well configuration, as
proposed by Zhu et al. (2015) for secondary recovery in a tight formation.  The proposed configuration uses alternately
distributed injection and production fractures along a horizontal well, to
create an array of plane-to-plane displacements in a single well.  Figure 1 illustrates a portion of the
envisioned well.

Figure 1: Single well injection and production

In this
work we propose a dual tubing system in the wellbore, with one tubing for
production and the other for injection.  The
injection and production sections would be separated with packers.  Figure 2 shows a diagram of a
completion configuration with these features.  The nature of the hydraulic communication
between injection and production fractures is essential to successful well optimization.
 The proposed optimization considers
production and injection sensors and controls for each fracture with capability
to shut off flow from any fracture with excessive CO₂ injection or production.

Figure 2: Completion configuration

In this
research, we are replacing the capacitance-resistance model (CRM) (Yousef, et
al., 2015) suited to water injection with a process control-relevant model, capable
of representing compressible flow in the reservoir. Then we are using this
model to forecast displacements along the well and anticipate what the
injection and production sensors would record under prescribed total well
injection rate and production pressure controls.

The
initially described well configuration likely has more sensors and/or controls
than necessary.  Once we understand
optimization with sensors and controls on every fracture, we will study how to
reduce the sensor and control requirements, for complexity reduction without
compromising recovery.  The ultimate goal
is a cost-effective well configuration likely to greatly increase recovery factors
currently common in tight oil wells.

References:

Yousef,
A. A., Gentil, P. H., Jensen, J. L., & Lake, L.
W. (2005, January 1). A Capacitance Model to Infer Interwell
Connectivity from Production and Injection Rate Fluctuations. Society of
Petroleum Engineers. doi:10.2118/95322-MS

Zhu, P., Balhoff, M. T., & Mohanty, K.
K. (2015, September 28). Simulation of Fracture-to-Fracture Gas Injection in an
Oil-Rich Shale. Society of Petroleum Engineers. doi:10.2118/175131-MS