Primary recovery mechanisms

UNIVERSIDAD DE ORIENTE
NÚCLEO DE MONAGAS
Escuela de Ingeniería de Petróleo
Inglés Instrumental IV

Primary Recovery Mechanisms

Section 01
Professor: Members:
Peters, GinaOjeda B. Alejandro


Maturín, January 2011

CONTENTS

Pg.
INTRODUCTION…………………………………………………………………….3

Primary Recovery Mechanisms ……………………………………………….4

Rock and liquid expansion drive…………………………………………………...4
Depletiondrive………………………………………………………………………..….5
Gas cap drive……………………………………………………………………………....6

CONCLUSION…………………………………………………………………………8

BYBLIOGRAPHY …………………………………………………………………...9

INTRODUCTION

Each reservoir is composed of a unique combination of geometric form, geological rock properties, fluid characteristics, and primary drive mechanism.

Although no two reservoirs are identical in all aspects, they can be grouped according to the primaryrecovery mechanism by which they produce. It has been observed that each drive mechanism has certain typical performance characteristics in terms of:

● ultimate recovery factor;

● pressure decline rate;

● gas–oil ratio;

● water production.

The recovery of oil by any of the natural drive mechanisms is called “primary recovery.”

Primary Recovery Mechanisms

For a properunderstanding of reservoir behavior and predicting future performance, it is necessary to have knowledge of the driving mechanisms that control the behavior of fluids within reservoirs. The overall performance of oil reservoirs is largely determined by the nature of the energy, driving mechanism, available for moving the oil to the wellbore. There are basically tree driving mechanisms that provide thenatural energy necessary for oil recovery:
(1) rock and liquid expansion drive;
(2) depletion drive;
(3) gas cap drive;

These tree driving mechanisms are presented below.

The above characteristic trends occurring during the production life of depletion drive reservoirs are summarized below:

1. Rock and liquid expansion

As the reservoir pressure declines, the rock and fluids expanddue to their individual compressibilities. The reservoir rock compressibility is the result of two factors:
(1) Expansion of the individual rock grains, and
(2) Formation compaction.

As the expansion of the fluids and reduction in the pore volume occur with decreasing reservoir pressure, the crude oil and water will be forced out of the pore space to the wellbore.

Because liquids androcks are only slightly compressible, the reservoir will experience a rapid pressure decline. This driving mechanism is considered the least efficient driving force and usually results in the recovery of only a small percentage of the total oil-in-place.

2. Depletion drive mechanism

This driving form may also be referred to by the following various terms:
● solution gas drive;
●dissolved gas drive;
● internal gas drive.

In this type of reservoir, the principal source of energy is a result of gas liberation from the crude oil and the subsequent expansion of the solution gas as the reservoir pressure is reduced. As pressure falls below the bubble point pressure, gas bubbles are liberated within the microscopic pore spaces. These bubbles expand and force the crude oil out ofthe pore space as shown conceptually in Figure 1. Cole (1969) suggests that a depletion drive reservoir can be identified by the following characteristics:

Pressure behavior:
The reservoir pressure declines rapidly and continuously. This reservoir pressure behavior is attributed to the fact that no extraneous fluids or gas caps are available to provide a...