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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