BASICS OF PETROLEUM RESERVOIR ENGINEERING
UNDERSTANDING OF
RESERVOIR ENGINEERING PIRSON:
"RESERVOIR
ENGINEERING MAY BE DEFINED AS THE ART OF FORECASTING THE FUTURE PERFORMANCE OF
A GEOLOGIC OIL AND / OR GAS RESERVOIR FROM WITH PRODUCTION IS OBTAIN ACCORDING
TO PROBABLE AND PREASSUMED CONDITIONS."
EXPLANATION
"Reservoir
Engineering" is a branch of "Petroleum Engineering" with its
main task is forecasting the behavior of the reservoir, the rate of production
and the amount of oil or gas that can be produced from a well, a group of
wells, or from all reservoirs, in the future based on possible assumptions , or
from existing past history.
The Modified McKelvey box shows resource status
categories.
Reservation
Estimation and Uncertainty
LIMITATION
- Estimates of oil and gas reserves under conditions of uncertainty.
- Definition of reserves and uncertainty.
- Technical, economic and political uncertainty.
- How to reduce uncertainty.
Definition
of Uncertainty: not necessarily happening, it has not been clearly defined,
without / lacking clarity.
Type of Uncertainty
- Technical, Economical, Political.
- Technical Uncertainty: geophysical, geological, petrophysical, or engineering risk.
- Economic Uncertainty: risk of price, capital and operating costs, profit sharing and taxes.
- Political uncertainty: country risk - governance stability, ownership status of oil production and (concessions, PSC, TAC, JOB, KKKS, etc ...)
Reservoir
Engineering
In
general, a "Reservoir Engineer" will relate to:
- Basic data, data on physical / chemical-chemical-physics, rock and reservoir fluid properties,
- Determination of the amount of reserves, both initial and remaining,
- Fluid flow in porous media,
- Well test, including: pressure test, productivity, communication between reservoir and / or layer,
- The behavior of the reservoir, future maintenance of reservoir behavior based on past behavior,
- Increased recovery,
- Economic analysis.
STAGE IN LEARNING
"RESERVOIR ENGINEERING"
Phase
I
Better
known as the basic introduction stage of reservoir technique, which addresses
reservoir techniques in general, the static and dynamic properties of rocks and
reservoir fluids, reservoir properties, permeability, fluid flow such as
pressure production rate and fluid pushing efficiency, saturation, capillary
pressure reflecting distribution fluid saturation in the reservoir,
compressibility which reflects the effect of changes in pressure on both fluid
and rock.
Phase
II
Known
as the basic application phase of reservoir engineering, it discusses the
definition of reserves and their calculations, the behavior of reservoirs and
the application of fluid flow equations in porous media, phasing out reservoir
production.
Stage
III
Known
as a further application of reservoir techniques, it discusses the analysis and
interpretation of fluid flow equations in porous media such as well tests.
Stage
III
Known
as the "RESERVOIR SIMULATION" stage
Reservoir
Engineering
1. Reservoir Limits
Reservoir
boundary is the dividing boundary between hydrocarbon areas and non-hydrocarbon
areas, which can be:
- Geological boundary
- Limits of differences in hydrocarbon fluids, such as water oil limits, gas-water boundaries, or gas-oil boundaries.
2. Reservoir Clarification based on geological traps
- Trap Structure
- Stratigraphic Traps
- Combination Traps
3. Level / degree of reservoir heterogeneity
- Uniform and non-uniform
- Homogeneous and heterogeneous
- Isotropic and un-isotropic
4. Reservoir classification based on fluids
- Oil Reservoir: black oil, volatile oil
- Reservoir Gas: dry gas and wet gas
5. Reservoir classification based on initial pressure
- Undersaturated Reservoir
- Saturated Reservoir
6. Reservoir classification based on the driving mechanism
- Soluton gas drive
- Gas cap drive
- Water drive
- Combination drive
7. Plans and types of tests to be carried out according to the
type of reservoir.
8. Plan for reservoir development, drainage patterns related to
the location of the production and injection time, number of wells, etc.
9. Plan for drainage of reservoirs and stages of production
- Primary production (natural depletion)
- Secondary recovery (water or gas injection)
- Tertiary recovery (enhanced oil recovery)
Reserves
IOIP/ IGIP (initial
oil in place / initial gas in place)
Is
the amount of oil or gas in a reservoir that is calculated volumetically based
on geological data as well as drilling, or material balance based on physical
properties of fluid and production reservoir rock and reservoir behavior, or it
can also be done by calculation of reservoir simulation.
Reserves
1.
Proven Reserves:
The
amount of hydrocarbon fluid that can be produced which amount can
proven
by a high degree of certainty.
- The results of log reliable qualitative analysis
- Successful content research and testing
- Can produce at a commercial production level
2.
Potential Reserves (Probable and Possible):
This
reserve is based on a geological map and still requires research with further
drilling.
HOW TO APPLY OIL
RESERVES
RESERVE
CLASSIFICATION
Type of Estimated
Reserves
- Deterministic Based Reserves Estimates - each parameter uses the best assumption.
- Probabilistic Based Reserves Estimates - quantification of uncertainty.
Reliability
of Reserves Estimates
- Data quantity and quality
- Competence and Integrity Reservation Estimator
Proved Reserves
Guidelines
- Known Reservoir
- Existing Economic and Operating Conditions
- Actual Production or Conclusive Formation Test
- Improved Recovery under Certain Conditions
- How to Incorporate New Technology
KNOWN
RESERVOIRS
- Penetrated by a Wellbore and Confirmed as Hydrocarbon - Bearing.
- Downdip Limits - Contacts or Low Known Hydrocarbons - example.
- Known Areas
- Fault limitations and distance between wells.
Effect of Economic
Calculations on Estimated Reserves
- Prices and Cost as of the Date of Reserves Estimate. Price Change Only as a Allowed Contractual Agreement - no escalations based on future conditions.
- Existing Operating Conditions and Equipment in place, and limited to economically feasible projects and "state-of-the-art" technology.
Production or
Testing Requirements for Proved Reserves
- Formation Test
- Drill-Stem Test (DST)
- Conclusive Formation Test
- FavorableWell Log Response or Core Analysis
Determination of
Production Phase
a.
Early Stage Production (primary)
- Naturally, that is production which occurs because the reservoir energy is able to lift fluid to the surface.
- Artificial lift, still using the reservoir energy coupled with external force (for example a bobbin pump, the pump subsides) or by reducing the weight of the liquid in the well column (for example with a gaslift).
b.
Second Stage Production (Secondary)
- Maintain stability and / or add energy to the reservoir directly by injecting water or gas in a well, then producing it from another well.
c.
Advanced Stage Production (Enhanced Oil Recovery)
- Heat injection: huff puff, steam (steam), in situ combustion
- Injection of materials: chemicals, surfactants, polymers
- Miscible injection: C02 or N2 gas
Reservoir Simulation
Reservoir
simulation is one method used to:
1.
Estimating the contents of the initial gas oil in the reservoir.
2.
Large identification and influence of aquifers.
3.
Identify the effect of faults in the reservoir.
4.
Estimating fluid distribution.
5.
Identify vertical relationships between layers.
6.
Production forecasting for the future.
7.
Production forecasting by including alternative development:
- Amount of addition of production wells
- Types / ways to increase production
- Amount of addition of injection wells
- System / shape / pattern area
8.
Make several cases to optimize oil production
Simulation
is a reservoir form / model that is mathematically elaborated. Where the model
is made and considered as the actual situation, in accordance with existing
reservoir parameters, or reliable assumptions.
Simulation Equipment
- Hardware (computers and their peripherals)
- Software (simulator)
- Reservoir as a model
Simulation
Implementation Steps
- Data preparation
- Initialization
- Alignment
- Forecasting
- Economy
Simulator type
- 1 Phase (gas reservoir)
- Black Oil Model
- Compositional Model
- Miscible Model
Some examples of Reservoir Simulator
Reference:
- Wahyono Kuswo, 2008, Dasar-Dasar Teknik Reservoir Migas, Ikatan Ahli Teknik Perminyakan Indonesia (Iatmi)
- S. Naji, Hassan Dr., 2004, Petroleum Reserves Estimation Methods, A Report Submitted to the Energy Studies Department OPEC Secretariat
- www.petrobjects.com
