Tripoli UniversityPetroleum Engineering Department

WATER CONING

spring 2013

contentsIntroduction Definitions

Critical rate correlations Vertical wells

Water coning treatmentConclusionReferences

Main Factors Coning Reduction methods

horizontal wells

INTRODUCTION

Coning: Coning or cresting is term used to describe the mechanism underlying the upward movement of water and/or the down movement of gas into the perforations of a production well.

Coning is primarily the result of movement of reservoir fluids In the direction of least resistance, balanced by a tendency of The fluids to maintain gravity equilibrium.

Critical production rate (Qoc): Critical production rate (Qoc) is define as the maximum allowable oil

flow rate that can be imposed on the well to avoid a cone breakthrough. Break through time(tbT):

Critical flow rate calculations frequently show low rates that, for economic reasons, cannot be imposed on production wells. Therefore, if a well produces above its critical rate, the cone will break through after a given time period. This time is called time to breakthrough tbT.y

Main factors effect water coning

Density different

Viscosity of water

Formation permeabilit

y

Pressure drawdown Flow rate Capillary

force

Water coning could be reduced by:

1\ decreasing flow rate

2\ improve productivity

3\ Use horizontal wells instead of vertical wells

4\ penetrate the well at the top of the formation

5\ Recompleting the well

6\ infill drilling

Critical Rate Correlations

Categories• many correlations have

been developed to determine the critical rate. In general, these correlations can be divided into Two Categories:

Analytically •the first category determines critical rate Analytically based on the equilibrium conditions of gravitational and viscous forces.

Correlation•The second category determines critical rate through empirical Correlations from experiments/simulations.

Most of the research efforts in the area of water and gas coning have concentrated on estimating the critical oil rate and the post breakthrough well

behavior

Vertical Well Critical Rate Correlations

Horizontal Well Critical Rate Correlations

Meyer-GarderHoyland-Papatzacos-SkjaevelandChierici-CiucciChaney et al.ChapersonSchols

Chaperson’s MethodEfros’ MethodKarcher’s Method Joshi’s Method

Assumptions of all correlations.

Homogeneous.

Radial flow.

Capillary pressures are neglected.

The Meyer-Garder Correlation

Meyer and Garder (1954) suggest that coning development is a result of the radial flow of the oil and associated pressure sink around the well-bore.

Vertical Well Critical Rate Correlations

The Hoyland-Papatzacos-Skjaeveland Methods

Hoyland, Papatzacos, and Skjaeveland (1989) presented two methods for predicting critical oil rate

The Analytical Solution Method

The authors presented an analytical solution that is based on the Muskat-Wyckoff (1953) theory. In a steady-state flow condition

The authors correlated the dimensionless critical rate (qCD)with the dimensionless radius (rDe) and the fractional well penetration ratio (hP/h)

Illustration of the boundary condition for analytical solution

Critical rate correlation

The Numerical Solution Method

Based on a large number of simulation runs with more than 50 criticalrate values, the authors used a regression analysis routine to develop thefollowing relationships:

• For isotropic reservoirs with kh =kv , the following expression is proposed:

• For anisotropic reservoirs, the authors correlated the dimensionless critical rate with the dimensionless radius rD and five different fractional well penetrations. The correlation is presented in a graphical form

Break through time in vertical wells

Based on laboratory data and modeling results

Dimensionless cone height Z

Dimensionless breakthrough time (tD)BT

Break through time (days)

Based on experimental data

o Dimensionless cone height Z

Dimensionless breakthrough time (tD)BT

Break through time (days)

The Sobocinski-Cornelius Method(1965) The Bournazel-Jeanson Method(1971)

Horizontal Well Critical Rate Correlations

Chaperson’s Method

Chaperson (1986) provides a simple and practical estimate or the critical rate under steady-state or pseudo steady state flowing conditions for an isotropic formation.

Efros’ Method

Efros (1963) proposed a critical flow rate correlation that is based on the assumption that the critical rate is nearly independent of drainage radius. The correlation does not account for the effect of the vertical permeability.

Break through time in horizontal wells

o proposed a theoretical correlation for calculating time to breakthrough in a bottom-water-drive reservoir

The Ozkan-Raghavan Method(1988)

Water Coning Treatment

Current state of Gel Technology:

Gel behavior mechanism for reducing water production:

Blocking the high permeability zonesProfile modification.Reduction in water to oil mobility.

Down-Hole Water Sink Technology

DWS water drainage-productionDWS water drainage-injection

Down hole Water Sink (DWS) is a completion/production technique for producing water-free hydrocarbons from reservoirs with bottom water drive and strong tendency to water coning.

conclusion1- Coning of water into an oil well occurs when the flowing

pressure gradients established around the well bore cause the water to flow across the bedding planes.

2- The drainage radius has a negligible impact on the critical rate predictions.

3- After water breakthrough in the well bore, water production increase rapidly and efforts have to be put into water disposed and oil / water separation facilities.

4- No consistency between the critical oil rate predict by the investigated empirical correlations, especially at high values of thickness, horizontal permeability and permeability ratio.

References

Reservoir engineering handbook, by Tarek Ahmed

Water coning phenomenon in oil fields; by emnani Mohammed Alzorgani.

well completions , work over , and stimulation by Thomas O. Allen & Alan P. Roberts.

Thanks for your Attention