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

Petroleum Drilling & Well Completion - An Overview

Petroleum Drilling & Well Completion

Petroleum Drilling commonly comprises The Drilling Preparations consist of The Rigs type, Drilling Procedures and Engineering Challenges, the Aim, Conditions location, And Drilling Program, Location Accessibility, Tools and Equipment, then The Rigs Systems Elements And Proses comprises The Rotating System, The Hoisting System, The Circulating System, The Prime Mover, Pressure Control System. Drilling Crew and Personnel’s consist of The Rigs Operating Crew, The Support Personnel’s. Then Routine Drilling Procedures such Drilling A Head, Making Connection, Round Tripping, Formation Drilling Data, Well Logging Operations, and MWD, LWD & SWD.

Well completion means preparing the well for production, of course well completion is worded only when the well have sufficient amount of oil and gas to be commercially viable. In running casing and cement the initial cementing called primary cementing creates a sheet or cover of hard cement that fills the annulus space between the outside of casing and the well bore well. Its primary function is to block fluid movement and pressure transmission up or down and the annulus, subsequent cementing is called squeeze cementing, and it’s done to repair the primary cementing or in connection with a work over a well that is being rework because of declining production.

The Process of Running Cement

The process of running cement, first dry cement is mixed with additives made up of accelerators, retarders, and density adjusters. The function of these additives is to adjust the dry cement properties to fit the conditions of the well, accelerator speed up the setting time of the cement, retarders to the opposite they prevent premature setting in deep high temperature well. Density adjusters increase the cement weight to reduce pumping pressures or to permit a higher cement column without fracturing the formation.

After the casing in place, the cement is properly blended with water and the hole does prepared for pumping, first a hard rubber rupture plug is inserted into the casing followed by the cement slurry, this plug will separate existing mud from the new cement. Pumps to the bottom of the hole the cement slurry pushing the plug in front as it flows down forces the rupture plug into the seat in the float collar. Once in place the driller slightly increases the well pressure to break through this rupture plug. Once the plugs broken the cement slurry displaces the existing mud in the annulus, when adequate cement has been pumped a second plug called seal plug is then inserted. This seal plug serves the separate the cement slurry from the fresh mud that follows. Finally the cement slurry is displaced out of the casing into the annulus. The cement job was completed when the second plug the seal plug land in seats in the grooves in the floats valve, this landing is signal at the surface by a sharp pressure increase. The pumps are then shut down which allows the pressure to drop.

The decreasing pressure causes the flow valve to close preventing the heavier cement in the annulus from running back into the casing. After the pumps or shut down well operations or suspended for from twelve to twenty four (12-24) hours, so the cement can set.

PERFORATING

With the cemented casing in place the next task is to perforate the casing in the zone of interest, called the pay zone. Perforating mean blasting through the walls of the casing, the cement sheets and continuing on for about one (1) meter into the formation rock, it is through these holes that hydrocarbon fluids will pass to the surface when production begins (Pic. 44). To blast through the casing and cement jet perforator are set to 4-8 holes per foot, each shot is rotated ninety (90) degrees or one hundred eighty (180) degrees from the one above throughout the pay zone, to blast these jet perforators through the casing and into the formation, casing guns are used. The retrievable and reusable these casing guns are made of strong wing constructed steel which are run with an electric wireline.

Before first firing, the gun and the hole is filled with salt water. This salt water is called water blanket or load brine, when the well has perforated the water rush out through the new perforations killing the well and preventing a blow up. With the potential for further damaging the formation near the wellbore using over balance conditions the engineering team made decided to stop for the perforations until the world has been prepared for production. This means that the well will be outfitted with tubing packers and the Christmas tree there accommodate perforating in underbalanced conditions. In addition many of the subsequent well treatment processes described, then the next segment of this book are optimally done after the well has been outfitted with these three components, they include the wellhead and the various processes of preparing a well for production and will be discussed here. In preparing the well for production smaller diameter pipe, called tubing is installed down the casing with a packers at the bottom. Let we point out here that the permanent casing is rarely used as a conduit to get oil and gas to the surface. Remember it's main function along with the annulus is to seal the wellbore and keep it sealed.

TUBING

Instead smaller tubing installed through the casing is used to bring the fluids to the surface. Manufactured in joints a thirty (30) feet with threaded couplings the diameter of tubing can vary, depending the fluid amount projected to be produce. For example small tubing that is to and three eight 35 inches 2 3/8” outside diameter is used for shallow low productivity wells. While large six inch 6” outside diameter tubing is used in high volume gas well.

In any case tubing is smaller than either the drilling casing pipe and is relatively lightweight when compared to them, because of two the smaller size and weight it can be run in and out of the hole by work over rig out fit with small or a hoisting equipment when you would find any drilling rig.

Here you can see that these strings hang from the tubing hanger in the wellhead and irretrievable unlike the permanent casing strings. Keep in mind also that although only one set of casing is ever run tubing because of its smaller size can be run through the casing and single, dual or multiple strings.

CHRISTMAS TREE

Finally a Christmas tree is installed, containing valve manifold that controls flow in the tubing, they must be strongly constructed to contain full of reservoir pressure, a christmas tree function is to control the pressure. In the illustration, the main valves that control the well pressure or labeled, they are choke, master valve, crown valve, the wing valve, and the safety wing valve.

Youtube:

References:

• Google.com
• Youtube.com
• https://www.amazon.com/PETROLEUM-DRILLING-OVERVIEW-Andi-Anriansyah/dp/1792194684
• https://www.amazon.com/PETROLEUM-WELL-COMPLETION-OVERVIEW-1/dp/1792195575