Monday, 31 August 2020

RIG INSPECTION GUIDELINES | CHOCK MANIFOLD ACCEPTANCE PRESSURE TEST

The Rig Accepting Process For The Choke Manifold Pressure Test

CHOKE MANIFOLD pressure test

Objective

  1. Explain the components, design & application of the choke manifold.
  2. Explain the purpose of the rig accepting for choke manifold 
  3. Explain the procedures for the rig accepting process for the choke manifold

Choke Manifold

Before going into the rig accepting for rig choke manifold, we have to identify the choke manifold.

The choke manifold is consist of a group of valves, lines, and chokes which are lined in a way to control any flow of drilling mud and Kick fluids from the annulus during any Well Control issue. Some of the conditions that the manifold may be required upon to work under are a variety of fluids such as Water Based MudOil Based Mud, water, or gas, high pressures, downstream velocities, upstream flow rates,  and obstructions in the produced fluids such as sand, pipe protector rubbers or shale.

The choke manifold should make a control on pressures by utilizing one of many chokes. It should direct flow to one of many areas including a burning boom, the reserve pit, drilling fluids pit, or overboard a drilling vessel when applicable. The choke manifold must have pressure ratings at least equal to the BOP stack and should have same pressure testing specifications which performed on the BOPs. It should be well fixed to prevent movement during any Killing operation. Also The choke manifold should have an easy access to every manifold component, with all lines fixed as straight as possible. All lines and valves must have equivalent consistent inner diameter to decrease turbulent erosion at any diameter changes.

Choke Manifold Design. 

The principle used for BOP stack design will also be used for designing the choke manifold. The proper procedure is to make sure that there are a backup system in case of tool fail. Also it is a good practice initially to utilize the manifold necessary to reach the total depth to avoid fixing a different manifold with each casing run in the hole. Below figure shows a choke manifold utilized in many drilling wells. Note that such design meets all of the needs for choke manifolds.

Typical choke manifold design (Courtesy Cameron Iron Works
Typical choke manifold design (Courtesy Cameron Iron Works


  • Buffer chambers are used at the downstream connections to be used as hydraulic cushions and to reduce erosion. 
  • Two hand-adjustable chokes may be used due to their high stem and seat erosion rates and due to their tendency to pack off with cuttings. 
  • A direct line from the BOP stack to the burning pit for gas is provided should it become necessary to divert the well temporarily. 
  • A current, and more appropriate, practice is to utilize two remote hydraulic adjustable chokes and a single manual choke. 
  • A tap may be used to allow for manifold pressurization to decrease pressure surges to zero when opening the valves near the stack. 
  • Note that this design does not constitute a true diverter system.
Below video can describe well what is the choke manifold and its application.


Choke Manifold Application

  1. A choke manifold is used to control the pressures encountered during a Kick 
  2. In well testing, a choke manifold attached to the wellhead allows flow and pressure control for test components downstream

Purpose Of Rig Accepting For Choke Manifold Pressure Test

  1. Verify the hydraulic integrity of all the components of the choke manifold at their rated  working pressure.

What is The Procedure For Rig Accepting The Choke Manifold Pressure Test

  1. Connect the testing pump or cement unit, with pressure recorder, to the choke manifold  inlet.
  2. Pump water through the choke manifold for some minute to flush all lines and purge it  from air.
  3. Close the first valve after the inlet; pump to reach the working pressure, hold  the pressure  for, 10 minutes.
  4. If the test is satisfactory continue the test of all the other components in cascade, from inlet(s) to low pressure buffer.
  5. Pressure test the flare lines installing a plug at the end of each line.
  6. Fill in the following table and attach the choke manifold drawing to the test report with references to all components.
choke manifold pressure test

Checklist To be In Mind While Rig Accepting Chock Manifold

  • Manifolds sizes and working pressure as per specifications
  • Manifold and valves easily accessible and free of obstruction
  • Valves wheels turn easily
  • Pressure gauges installed and calibration is documented
  • Manifolds provided with connections for tranducers
  • Casing and drill pipe pressure gauges installed and calibration documented
  • Casing and drill pipe pressure gauges easily visible from manual choke operator's position
  • MAASP posted at manual choke
  • Safety chains / whipchecks used for pressure hoses, lines with hammer unions or chiksans, in temporary or permanent use 
  • Lines from BOP to choke manifold of the approved type 
  • Manual and power chokes at choke manifold as per approved number 
  • Lines and valves are free from mud or solid wastes and flushed with water
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