BASICS OF PETROLEUM RESERVOIR ENGINEERING

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