ABSTRACT
The design of natural flow and artificial lift tubing strings for the
whole life of a water drive reservoir was carried out using data based
on synthetic reservoir performance based on a material balance. The
effects of reservoir properties on the life of the well were also
investigated. Constraints such as maximum production, maximum drawdown,
limitations on surface facilities capacities, as well as available gas
lift were imposed.
The production conditions for natural flow, continuous gas lift, and
an ESP for later phases of the reservoir was designed and simulated
along time by imposing either a constant flow rate or a constant bottom
hole flowing pressure. A forecast of the production of oil and gas as
well as the time where tubing strings should be replaced as a function
of both the cumulative production and time was presented.
The work was concluded by reservoir pressure was maintained much
longer in comparison to other drive mechanism when there is an active
water drive preferably edge water drive reservoirs which maintains a
steady-flow condition for a long time before water breakthrough into the
well.
Finally the following areas were identified for improvement in the
development of the work one is that the assumptions in this work is the
use of synthetic reservoir performance data based on material balance a
possible extension is by incorporating more practical condition by
including more wells and the performance with time better analyzed and
further oil production economic analysis should be inclusive in the work
so that the optimum production pattern of the reservoir could be
determined.
CHAPTER ONE
INTRODUCTION
1.1 OVERVIEW
Fluids are stored in the reservoir and must be produced to the
surface facilities in order to be measured, treated and finally sold or
discarded. The flow of fluids from the reservoir towards the final
processing facility is divided into three phases: Recovery, Lift and
Gathering.
Recovery refers to the flow of fluids from the reservoir into the
well bore; Lift refers to the flow of fluids from the bottom of the well
bore to the surface wellhead and Gathering refers to the flow of fluids
from the wellhead through the gathering network towards the production
facility.
Recovery is used in a broader sense a referring to the production
including the lift and gathering processes. Lift and gathering process
will influence the final recovery of hydrocarbons and must be included
in a proper economic analysis.
The flow rate from a well depend on the energy level of the reservoir
and the energy losses of the fluids as they flow from the reservoir
towards the surface facilities. In order to increase production flow
rates we may use processes or systems to either increase the energy
level or to facilitate the flow of hydrocarbons. Those systems or
processes may be used in the reservoir or
in the production tubing or gathering system. The recovery of
hydrocarbons may then be classified as: Primary where no process or
method is used to increase energy level or facilitate the flow of
hydrocarbons inside the reservoir; Secondary and Tertiary where methods
are used to increase energy level and or to facilitate the flow of
hydrocarbons in the reservoir.
The lift and gathering may also be classified as: Natural flow – No
process or method used to increase energy level or facilitate the flow
of hydrocarbons in the production system; Artificial lift– when
processes are used to increase the energy level or facilitate the flow
of hydrocarbons inside the well bore; Boosting – When processes are used
to increase the energy level or facilitate the flow of hydrocarbons
downstream of the wellhead.
The recovery of hydrocarbons is classified in the following
categories: Primary Recovery (also called Primary Production); Secondary
Recovery (also called Secondary Production); Tertiary Recovery (also
called Tertiary Production or Enhanced – EOR or Enhanced Production or
Improved - IOR or Improved Production). Those categories are usually
associated with a method or recovery (or production) used - Primary
recovery uses the pressure and displacement of hydrocarbons without any
external process using solely the reservoir drive mechanism, secondary
recovery supplements the natural drive effects on pressure maintenance
and displacement by
water injection or water flood and natural gas injection ; and
Tertiary recovery supplements the natural drive by modifying the
properties of the fluids by chemical floods, miscible displacement and
thermal methods.
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 primary recovery 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.
The term refers to the production of hydrocarbons from a reservoir
without the use of any process (such as fluid injection) to supplement
the natural energy of the reservoir
For a proper understanding of reservoir behaviour and predicting
future performance, it is necessary to have knowledge of the driving
mechanisms that control the behaviour of fluids within reservoirs. The
overall performance of oil reservoirs is largely determined by the
nature of the energy, i.e., driving mechanism, available for moving the
oil to the well- bore. There are basically six driving mechanisms that
provide the natural energy necessary for oil recovery:
Rock and liquid expansion drive, Depletion drive, Gas cap drive, Water drive, Gravity drainage drive, Combination drive.
1.2 METHODOLOGY
In this work the design of natural flow and artificial lift tubing
strings for the whole life of a water drive reservoir will be carried
out using data based on synthetic reservoir performance based on a
material balance. The effects of reservoir properties on the life of the
well will also be investigated.
Constraints such as maximum production, maximum drawdown, limitations
on surface facilities capacities, as well as available gas lift and
horsepower will be imposed.