METODE DARCY

Asumsi = Aliran/fasa

     Stedy state

     Aliran radial

     Homogeny


 
Q = 7,08 . 10-3 K.h (Pr - Pwf)

    µ0 . Bo (ln re/rw + S – 0.75)


 
J = 7,08.10-3 k.h

    µ0 . Bo (ln re/rw + S-0,75)


 
Q =    J (Pr - Pwf)

Q =    PI (Pr-Pwf)


 
ket :     K : permeabilitas (MD)

    h : ketebalan formasi (Ft)

    Pr: tekanan reservoir (Psi)

    µ0: Viskositas oil (Cp/p)

    Pwf: tekanan air dasar sumur (Psi)

    Bo: Faktor volume formasi minyak (BBL/STB OIL)

    re: jari-jari pengurasan (acre)

    rw: jari-jari sumur (Ft)

    S : Skin (dimension)


 
IPR (INFLOW PERFORMANCE RELATIONSHIP)

Adalah perilaku aliran fluida dari reservoir ke dasar sumur. Hal ini terjadi pada kondisi alirannya 2 fasa.

Terjadinya aliran 2 fasa apabila adanya perubahan temperature dan tekanan dimana tekanan berada di bawah tekanan titik kritik (critical point).

Metode yang dilakukan pada IPR :

1. Vogel
   
2. Standing
   
3. Horizon
   
4. Fetkhovich
   
5. PS
   
6. Shell
   

 
IPR metode Vogel memiliki asumsi-asumsi sebagai berikut :

1. Aliran 2 fasa
   
2. No skin (ini adalah kelemahan Vogel)
   
3. Open hole
   
4. Steady state (bentuk aliran)
   
5. Homogeny (Radial)
   

 
Fungsi dari kurva IPR adalah untuk mengetahui kondisi sumur dengan mengetahui Pr, Qmax dan Pwf maka akan diperoleh Qo.

Yang membedakan metode IPR dengan ayang lain adalah :

1. Skin
   
2. Stedy state (aliran/jenis aliran)
   
3. Radius pengurasan
   

 
BERSAMBUNG……….

EQUIPMENT OFFSHORE DRILLING

A. PavilionType of platforms in general can be classified into two groups, namely1. Fixed platforms2. Mobile platform
1. Fixed PlatformFixed platforms are "mainland" artificial. Rigs are drilling platforms until the operation is complete. All equipment and material needs are in the platform. Fixed platforms are widely used for drilling operations in shallow seas, such as the North Sea Java. But now have been developed for deep ocean, for example in the North Sea.
2. Mobile PlatformsMobile platform is subdivided Bottom Supporting Platforms and Floating Platform.a. Bottom Supported PlatformsThe types of offshore drilling platforms are included in the category Bottom Supported Platforms includea. Drilling Bargeb. Sub-mersible Platformc. Jack Up Platforms
a. Drilling BargeDrilling barge operated for drilling in the area of ​​marsh or the sea is very shallow. Barge was sitting at the bottom of marshes or the sea, stability is not affected by the weather and tides.b. SubmersibleReal submersible floating platform. When operated in shallow seas, submersible is seated on the sea floor and serves as a drilling barge.c. Jack-UpForm a kind of jack-up barge, bulky and not have its own propeller, so to go to the location to be pulled by tugs. Jack-up is equipped with legs that consists of three, four, five feet or more. In the drilling position, the ship lifted on their feet, high enough above the water well above the reach of the waves. The depth of the sea in accordance with long legs so limited their use. Jack-up is stable, not affected by the weather, currents and waves. All equipment on board. In the drilling of development, usually before the drilling starts first fitted jacket, and then installed conductor and ground. In exploration drilling is typically used mudline suspension, and the mud line suspension chassis greeted upward until the platform.
b. Floating PlatformThe types of offshore drilling platforms that fall under this category include the Floating Platform Semi-submersible platform, and Drill Ship.- SemisubmersibleSemisubmersiible sort of boat-shaped and generally does not have its own propeller, so to get to the location to be pulled by tugs. Because it floats, so it can be influenced currents, waves and tides. To overcome these problems must dijangkar. Anchoring system there are two kinds, namely:· Conventional Mooring System· Dinamic Positioning
For completion wells can be done:· By Christmastree on Platform· By Christmastree on the seabed.
- Drill ShipDrill ship is fully ship shape and comes with its own propeller. Because it floats, so strongly influenced by currents, waves and tides. To overcome these effects should dijangkar like submarsible. BOP installed on the seabed and for completion wells can be made:     

      a) Christmastree on the seabed
      b) Christmastree on platform

HISTORY OF OFFSHORE DRILLING (Offshore Drilling)

In In 1891 the first oil drilling platform built on fresh water in the lake waters of St Marys in the state of Ohio, the United States. Then around 1896, the first oil well in the waters of the salt water was built as part of the extension of Summerland oil field across the bottom of the canal of Santa Barbara in California, USA. Wells drilled from the pier that extends from Summerland to the canal.

Foundation Simulation

Pile Modelling
 

In an offshore structure, the piles hold them on to the sea bed. This needs to be simulated
in the structural analysis involving their inplace strength and stability. There are type of
pile system that can be used in the o®shore structures.

1.  Main Pile
2.  Skirt Pile

As it can be seen from the ¯gure that the skirt pile is always grouted with the skirt sleeve
of the jacket. But in the case of main pile, the annulus between the pile and the jacket leg
may be grouted or not grouted depending on the design water depth. Like other structural
elements of the jacket structure, pile is also a structural member and shall be modelled
according to the diameter, wall thickness and material properties. It is the load transfer
mechanism between the jacket leg and pile that requires special care in simulation of actual
load transfer.

For the case of grouted skirt piles and main piles, the model becomes much easier by simply
specifying the cross section as a "Composite Section" containing jacket leg, pile and the
annulus ¯lled with cement grout. The equivalent axial area, shear area and bending sti®ness
can be calculated using the equivalent section concept and used in the analysis.
But for the case of main pile, this cannot be done. The pile and jacket are two parallel
members physically connected at the top of jacket by means welded connections and else
where no welding but spacers are placed inside the jacket leg to provide contact points for
load transfer. These spacers are specially located at the horizontal framing such that the
lateral loads from the wave and current can be easily transferred to the piles.

Soil Simulation

Piles below seabed shall be modelled in the structural analysis to reffect the vertical and
lateral behaviour of pile soil system. This is very essential to simulate the jacket and deck
de°ections and pile stresses. This can be done in three ways.

1.  Equivalent Pile Stub -
2.  P-Y, T-Z and Q-Z Curves -
3.  Linearised Pile Stiffness Matrix -

Pile Group EFfect
The skirt piles for very large jackets normally arranged in cluster at each corner to resist the
forces from gravity and environmental loads.
These pile clusters can be arranged in various ways but due to construction limitations
usually they will arranged in closed manner as shown in the Figures 5.10 and ??. The
distance between the jacket leg and the farthest pile shall be kept to a minimum possible for
fabrication to avoid unnecessary bending on jacket legs as well on the pile sleeves.
It is a good practice to space the centre to centre of adjacent piles at a distance of 3D
where D is the diameter of the pile. This will prove a clear distance between the pile face of
2D.Even with this separation, the effect of load on one pile will affect the behaviour of the

adjacent pile. The issues to be looked into are two categories as listed below.

•  EFect Axial Capacity
•  EFect on P-Y, T-Z and Q-Z behaviour

FLUID MECHANICS

Fluid mechanics is the sub-disciplines of continuum mechanics that studies fluids (which may include liquid and gas). Fluid mechanics fluid can be divided into static and dynamic fluid. Fluid static study the fluid at rest while the fluid moving fluid dynamic study (wikipedia).
Substance differentiate into three phases namely:
Solid phase is the substance retains a fixed shape and size, although a large work force on solid objects.
Liquid phase is the substance does not retain permanent shape but the shape of the container.
Gas phase is the substance has no fixed form or volume, but will grow to fill the entire container.
Because the liquid phase and gas does not maintain a fixed shape, both have the ability to flow with the so-called fluid.

 

ρ = m/v

m: mass of the object (kg)

v: volume (m3)

Density is the ratio of the density of the object is the density of water or quantities without dimensions or units.

Pascal's principle states that pressure is done in a fluid will cause the increase in pressure in all directions equally. So, with our small force that can be used to make cross-sectional area greater output from the input section.

The pressure in the fluid (P) is the force per unit area, with the force (F) is considered work perpendicular to the surface area (A)

P = F/A

P: pressure (Pa)
F: force (N)
A: cross-sectional area (m2)
 

Fluid using the pressure in all directions. At a certain point Dalan fluids at rest, pressure is the same for all directions. Pressure on one side must be equal * with pressure on the opposite side. If not the same, the number of forces acting will not move until the working pressure becomes equal.

Other properties of fluids at rest the force caused by fluid pressure is always working secra perpendicular to each surface of the touch.
The pressure in the fluid that has a uniform density will vary with depth.
Pressure caused by fluid in the depth (h), caused by the heavy fluid on top. So the forces acting on an area below the 

 

P = F/A = ρ.A.h.g/A = ρ.g.h

The equation P = ρ.gh can be used to determine the pressure difference, ΔP, at different depths with a density ρ average:

ΔP = ρ.g. Δh

• Fluid Dynamics
Discussing about the diataranya Fluid flow is:
Straight Flow (Streamline) or laminar flow occurs when the flow is smooth, so that adjacent layers of fluid flowing smoothly or Any particles that pass a point moves right along the path followed by other particles that pass through the previous point. Characteristics:
Streamline is the trajectory
o Streamline the different does not intersect
o Streamline at one point stating also the direction
fluid flow at that point

Turbulent flow or turbulent flow that is above a certain speed, which depends on a number of factors, the flow will be turbulent. This flow is characterized by uncertainty, a small, coiled like a whirlpool called Eddy currents or kisaran.Ciri-Characteristics:

1. The flow becomes indeterminate

• Not achieving a certain speed value
• Appears circumstances that led to changes
• speed suddenly
• Flow Eddy (vortex current)
  
  
  HYPOTHESIS KONTINIUM  
  Continuum Hypothesis is only a hypothesis which is basically just the approach. As a result, assuming the continuum hypothesis to provide results with accuracy levels that are not desired. However, if the conditions are right, the continuum hypothesis produces very accurate results. Fluid drawn up by the molecules collide with each other. However, the continuum assumption considers fluids to be continuous. In other words, properties such as density, pressure, temperature, and speed is considered undefined at points which are very small that define REV (''Reference Element Reference Element of Volume'')/(' Volume'') in order geometric distance between opposite molecules in the fluid. a fluid is incompressible the density of the fluid does not change when given the pressure. Sometimes fluid can be modeled as an incompressible fluid while all the gas could not. 

FLUID BY THE EXPERTS  
The Navier-Stokes (Claude-Louis Navier and George Gabriel Stokes) is a set of equations describing the motion of a fluid such as liquid and gas. These equations state that the change in momentum (acceleration) of fluid particles depend on the internal viscous forces and viscous forces of external pressure acting on the fluid. Therefore, the Navier-Stokes equations describe the balance of forces acting on the fluid. Newtonian fluid (named for Isaac Newton) is defined as fluid shear stress is linearly proportional to the gradient of velocity in the direction perpendicular to the shear field. Non-Newtonian Fluid Yang stirred, will remain a "hole". This hole will be filled over time. Such properties can be observed in materials such as pudding. Another event that occurs when non-Newtonian fluid is stirred viscosity reduction which causes the fluid looks "thinner" example: in the paint. 

UNITS AND DIMENSIONS Magnitude is anything that can be measured and expressed with numbers, such as length, area, volume, and speed. Dimension is a measure to declare variables of physics (Physics Variable) quantitatively. Dimensions in International Units (SI) Length: L Mass: M Time: T (S) Temperature: oC Dimensions in the British (BG) Style: F (Newton) Length: L (m3) Massa: T (S) Temperature: F

Unit Quantities Conversion Factor Angle 1 putaran = 3600 = 2 π rad Density 1 gm per cubic centimeter = 103 kg/m3 Berat air = 62,43 lb/ft3 Massa 1 kilogram = 103 gm = 6,85 x 10-2 slug 1 gram = 10-3 kg = 6,85 x 10-5 slug lengt 1 meter = 3,281 ft 1 foot = 0,3048 m 1 mile = 1609 m = 5280 ft 1 angstrom = 10-10 m Style 1 newton = 105 dyne = 0,225 lb 1 dyne = 10-5 N = 2,25 x 10-5 lb 1 pound = 4,448 N = 4,448 x 105 dyne Speed 1 meter/det = 3,281 ft/det = 2,237 ml/jam Pressure atm mmHg N/m2 Lb/ft2 Atm 1 760 1.013 x 105 2116 Mm air raksa 1,316 x 1013 1 133,3 2,785 N/m2 9,869 x 10-6 7,5 x 10-3 1 2,089 x 10-2 Lb/ft2 4,725 x 10-4 0,359 47,88 1 Energy 1 joule = 0,7376 ft-lb = 0,239 cal = 107 ergs 1 ft-lb = 1,356 J = 0,324 cal 1 cal = 4,186 J = 3,087 ft-lb Power 1 watt = 0,737 ft-lb/det = 1,341 x 1013 hp = 1 J/det 1 hp = 550 ft-lb/det = 746 watt 1 ft-lb/det = 1,818 x 10-3 hp = 1,356 W

SUBSEA

 

Subsea is a term used to refer to the equipment, technology, and methods used to explore, drill, development and operation of an oil and gas fields under the water surface. Able for areas that are shallow (shallow) or deep sea (deepwater). Subsea structures built in the sea to explore oil and gas that lies in a shallow sea and deep sea. Installation of subsea (offshore) depending on environmental conditions, as well as surface structure and require updating. Many of the reasons why in doing offshore drilling (offshore):  

1.Menemukan vast reserves of oil and gas fields and can be profitable. 2. Allows for producing from the deeper sea.
As well as things that may need to be noticed are:

1. Need high realibitas  

2. More complex subsea installations  

3. Some technology still in development.  

4. Factors to consider are the depth, tide, waves and currents, wind, earthquake and ice (North Sea).



Well many companies that do offshore drilling: 

1. Petrobras  

2. Statoil  

3. Shell  

4. Exxonmobile  

5. Bp  

6. Norsk Hydro  

7. Chevron  

8. Kerr-McGee  

9. Total  

10. Talisman
 

An estimated 5-10% of world oil reserves under the sea and is currently estimated to be around 30% of the total production comes from offshore oil and gas. So the development of subsea technology into one attractive alternative given the thinning reserves on land. The first offshore drilling done by the chevron is in california. And the deepest wells in the 2008 which was developed by teledo at bay mexico is 3050 m Operational Criteria
Determination of the bridge functions (drilling, production, storage, shelter engineer, etc.), the total number of wells drilled, total deck and equipment needed, and methods of oil and gas transportation is the work of multiple disciplines such as engineering geophysics and geology, oceanography, chemical engineering, mechanical engineering and electrical and instrumentation engineering, marine engineering, and environmental engineering. 

1. Stages of drilling

1.Explorasi Oil and gas exploration is done with the ship that uses the reflection wave to get beneath the surface seismic data. 

2.Drilling
A location has been selected and prepared, several holes dug to make a point of drilling equipment (rigs) and the main hole.
This operation is done to ensure the presence or absence
content of oil and gas. (Using the Jack-Up Rig)

COMPONENTS OFFSHORE PLATFORMS

1. Topsides
The top of the bridge as a place of all equipment (process, mechanical, electrical and instrument) for the drilling / production of oil and gas.
(other terminology: Deck, Upper Structure)
 

2. Supporting STRUCTURE
To support and protect decks / topsides of environmental burdens such as waves, currents, wind, and earthquake) (another term: substructure). 

-TREE
Its function is to control the flow of tree production from the well through several valves and chokes, to a manifold or elsewhere.

-JUMPERS / flowlines
Jumper is a very short spool (also can be rigid or flexible) so that it can be installed in a single generation into the seabed.

-Manifold
Which sends the results to the place of production and storage process which is usually located on top of floating or on land.
Based on the location of manifold:
1.Template manifold that is so one with the wells
2.Cluster manifold that is off-site wells
Based on the structure of the manifold:
`1. Integral manifold of a unified structure
2.Retrievable manifold of structures that can be taken back into the water.

-FTA (Flow Termination Assembly)
To connect the pipeline with other facilities, namely PLET, PLEM and Riser Base.

-Riser
To connect the flow from the seabed into the water. Riser base must be installed separately, so need two connectors for connecting the riser and pipeline.

-FPSO (Floating Production, Storage And Offloading)

 
What is meant by FPSO here is not just a boat-shaped, but also SPAR, TLP and other floating.
1. (TLP = Tension Led Platform) TLP = pavilion is part topsidesnya supported by columns, pontoons (hull) and tethered to the seabed by several fastening (tendons)
2. (SPAR = Spar is Deep draft floater (DDF), which is categorized as a relatively large power muatnya).
Tree mounted above the well and will be on stream by the manifold to be sent to storage (storage) in surface water usually fixed structures on the surface or on land. To connect the manifolds we need a tree with jumper / flowlines. If the storage place is too far in requiring the FTA at the downstream end of the manifold to the riser and forwarded by the riser to raise to the surface or to a FPSO (SPAR / TLP).