Types of Reservoir Drives


Types of Reservoir Drives


The reservoir drive mechanism supplies the energy that moves the hydrocarbon located in a reservoir container toward the wellbore as fluid is removed near the wellbore. There are five common drive mechanisms: Water drive, Gas expansion, Solution gas, Rock or compaction drive, Gravity drainage

One type usually dominates, but drive types can occur in combination. Depending on the drive mechanism, characteristic recovery efficiencies can be expected for a given reservoir.

1. Oil reservoirs.

a.     Solution gas drive.

b.     Gas cap drive.

c.      Water drive.

d.     Gravity drainage drive.

e.     Combination drive.

2. Gas reservoirs.

a.     Volumetric (gas expansion) drive

b.      Water drive

c.       Combination drive


Gas Cap Drive

At initial conditions, the reservoir fluid is saturated. The bubble point pressure can be measured in the reservoir at the depth of the GOC.

Types of Reservoir Drives
gas cap drive

As pressure falls, energy is created both by liberation of dissolved gas and  by expansion of the gas cap.
 The driving action of the gas cap pushes oil down structure ahead of the expanding gas cap.
 Fluid contacts must be closely monitored to avoid invasion of the oil column by the gas.
Reservoir pressure drops relatively slowly because of the compressibility of the gas. GOR will only increase with breakthrough of gas in production  wells.

Reservoirs tend to flow longer at more stable pressures. Oil rates are sustained by the slow driving force of the expanding gas.



IPR


Solution Gas Drive: Reservoir Energy

At initial conditions, a pure solution gas drive reservoir has no gas cap nor an aquifer. The main source of energy is the liberation of solution gas under the effect of pressure reduction. The expansion of the gas pushes the oil downward and radially into the wells. Other sources of energy (rock, oil and connate water compressibility) are usually minor. Liberated dissolved gas may segregate from the oil phase under gravity forces, and form a secondary gas cap.

Production Characteristics:

The initial GOR is at or below the solution GOR.  The oil rate drops rapidly as gas starts to breakthrough in the reservoir and forms a continuous phase. The pressure decreases rapidly until total virtual depletion.
When pressure becomes very low, Bg approaches 1 and surface gas rates decrease correspondingly. This causes a sharp reduction in the GOR.

Secondary Gas Cap:

Liberated solution gas may be pulled into a producing well at high oil production rates. Liberated solution gas may also move up structure and form  a secondary gas cap in cases of:
·        low oil producing rates.
·         low oil density.
·         high reservoir dip angle.
·         high permeability.
Summary
·        The reservoir pressure declines rapidly and continuously, then flattens out.
·        The surface GOR is initially low, then rises to a maximum and drops from then on.
·        There is no water production unless an aquifer is present.
·        The well requires artificial lift at an early stage.
·        The expected primary oil recovery is in the range of 5% to 30% of the oil.

Water Drive


Reservoir pressure declines slowly. In artesian drives, the pressure remains constant and equal to the hydrostatic value. Gas-oil ratio is limited because the pressure stays high. Oil rate declines slowly. Water-cut increases gradually, and can be as high as 90% or more in the mature life of the reservoir.

Gravity Drainage

Gravitational segregation is the tendency of fluids in reservoir to segregate, under the influence of gravity, to vertically position themselves as dictated by their respective densities (gas above oil, oil above water). Gravity drainage may occur in any type of reservoir. Gravity drainage is particularly important in solution-gas and gas-cap drive oil reservoirs.

 Combination Drive

Most reservoirs do not produce from a single source of energy and by a single mechanism. The ‘combination drive’ is the most frequent occurrence. In a combination drive, both a gas cap and an aquifer are present. Energy available includes influx from the aquifer, gas cap expansion, oil expansion and even evolution of the solution gas. Rock decompression may also play a role.


Reservoir drive

keywords: gas drive, water drive, types.

Comments

Post a Comment

Popular posts from this blog

Gas-Lift Troubleshooting

Image
Troubleshoot your well before you call a rig. Gas-lift problems are usually associated with three areas: inlet, outlet, and downhole (Fig. 1). Examples of inlet problems may be the input choke sized too large or too small, fluctuating line pressure, plugged choke, etc. Outlet problems could be high backpressure because of a flowline choke, a closed or partially closed wing or master valve, or a plugged flowline. Downhole problems could include a cutout valve, restrictions in the tubing string, or sand-covered perforations. Further examples of each problem area are included in this handbook. Often the problem can be found Fig. 1: The Gas-Lift System on the surface. If nothing is found on the surface, a check can then be made to determine whether the downhole problems are wellbore problems or equipment problems. Inlet Problems Choke sized too large .  Check for casing pressure a...
Read more

Lecture about Porosity in Reservoir Rocks PPT

Image
Understanding Porosity in Reservoir Rocks Porosity  is a critical rock property in the oil and gas industry. It defines the fraction of a rock’s volume that is occupied by pore space—those tiny voids where fluids (such as oil, gas, and water) can reside. Imagine these pores as the reservoir’s storage compartments, waiting to hold hydrocarbons. Understanding Porosity in Reservoir Rocks The Basics of Porosity 1. Definition:   Porosity quantifies the storage capacity of a rock. It’s the ratio of the pore volume to the total volume (also known as the bulk volume). Mathematically, we express it as:   [ \phi = \frac{{V_p}}{{V_b}} ]   Here: (V_p) represents the pore volume. (V_b) is the bulk rock volume. 2. Types of Porosity: Total Porosity ((\phi_t)): This includes both connected and isolated pores. Connected pores can transmit fluids, while isolated pores cannot. Effective Porosity   ((\phi_e)): Only considers connected pores—the ones that matter for fluid flow....
Read more

Introduction to Reservoir Rock Properties - Lecture in PPT Format

Image
Introduction to the Properties of Oil Reservoir Rocks: Definitions, Reservoir Types, and Oil Traps Introduction to the Properties of Oil Reservoir Rocks: Definitions, Reservoir Types, and Oil Traps Oil reservoirs play a pivotal role in the global energy supply, and understanding the properties of reservoir rocks is crucial for successful oil exploration and production. This lecture offers a comprehensive introduction to the essential characteristics of oil reservoirs , from fundamental oil-related definitions to the types of rocks and structures involved in oil trapping. Whether you are a student, geologist, or petroleum engineer, this guide serves as an important resource for grasping the geological factors that influence oil reservoirs . In this lecture, we delve into several key topics: Introduction to Oil Reservoir Properties This section provides a clear understanding of what oil reservoirs are and their significance in the petroleum industry. We explain the physical and chemic...
Read more