Thursday, 27 August 2020

RIG INSPECTION GUIDELINES | CEMENTING UNIT ACCEPTANCE INSPECTION

Cementing Unit Acceptance Inspection

Cementing Unit Rig Acceptance Inspection

Cementing Unit:

The cementing unit is a high-pressure pump which used to force cement down the casing and into the annular & space between the casing and the wall of the open hole.

Cementing units usually adapted with mixers, pumps & drives to provide on-site cement mixing and injection inside the well, especially to oil and gas drilling operations. The cementing operations prevents water invasion into the drilled well, provide isolation to the annulus after running casing string, and also can be used to pump & set a cement plugs to isolate certain zones or shut in the well.

Cementing units shall be able to provide an acceptable range of pressures and pumping rates to provide the requirements of recent cementing practices, and off course have the lowest applicable weight-to-horsepower ratio to facilitate transportation.

Cementing Unit Components:

To understand the inspection process of such cementing unit, we will have to go through the cementing unit components.

Cementing units are usually prepared with two positive-displacement pumps. 
  • For a high-pressure system, one pump mixes the cement while the other pump push the cement inside the well. 
  • For a low-pressure system, a centrifugal pump is used to mixes the slurry, and two positive-displacement pumps are used for displacement. 
  • For recirculating mixing, one centrifugal pump provides water to the mixing jet, and another centrifugal pump recirculates slurry back through the mixing jet. As with a low-pressure system, two positive-displacement pumps are used to get the slurry and displace it down the well.

Motor, transmission, and pumps: 

A heavy-duty electric powered engine or petrol related to a transmission supply mechanical energy to drilling mud pumps and water pumps, in addition to the agitator.

Mostly all the cementing pumps are positive-displacement pumps, and it is common to find it duplex double-acting piston pumps or single-acting triplex plunger pumps. Either is satisfactory within its design limits. For heavy-duty pumping, triplex pumps discharge more smoothly, and can usually handle higher horsepower and greater pressure than duplex pumps. Most cementing work involves a maximum pressure of less than 5,000 psi, but pressures as high as 20,000 psi are not uncommon. Because of widely varying operating conditions, the cementing pump and its power train are designed for the maximum rather than the average expected pressures.

Mounting platform: 

cementing units utilized in the oilfield can be trailer-mounted or truck-mounted. Cementing units can be established on skids, which cause them to be greater appropriate for in-situ applications, such as in marine drilling rigs. Also it can be mounted on waterborne vessel.

Control system: 

The cementing operator has panel-mounted controls so he can easily adjust flow rate, cement slurry density, and different cementing unit parameters. A lot of cementing units include hydraulic and digital gauges to help operators to observe all cementing operations.

The Mixing System: 

Water and cement slurry reservoirs converge in the mixing tank earlier than being dispensed via unit outlets and hoses through pumps. A cleaning system are able to clean any remaining cement slurry.

The cementing job determines which sort of cementing unit will be more applicable. A modular design is favorable for oil rigs, because it have to meet size, safety, and power constraints.

Purposes of Cementing Unit Inspection Test

  1. Verify the hydraulic integrity of Cementing Unit, cementing lines and cementing manifold at  the maximum working pressure. 
  2. Verify the flow rate, the mixing and power capability of the Unit. 

Guideline for Cementing  Unit Pressure Test.

  1. If the Drilling Contractor has its own procedure follows those procedures. 
  2. Be sure that all the components of the Cementing Unit are pressure tested to the working pressure: 
    1. Cement unit manifold, 
    2. Cementing lines, 
    3. Rig floor cementing manifold. 
  3. Attach to the report a schematic drawing of the cementing manifold system with the result of the test 

Guideline for Cementing Unit Flow rate tests.

  1. Fill up the two tanks of the cementing unit with water. 
  2. With one pump start pumping at the maximum flow-rate possible taking water from each of the cementing unit tanks alternatively and refilling the empty tank with the rig centrifugal pumps. 
  3. Repeat the same operation with the other pump of the cement unit.
  4. Repeat, if possible,  the same operation with the two pumps together.
  5. Fill in the following table.
Cementing Unit Acceptance Inspection

Other Items To Put In Mind While Rig Accepting For Cement Unit

CEMENTING UNIT : 

1 State of maintenance satisfactory : 
2 Date of unit last general overhaul : 

Cementing unit discharging lines 

1 Number and dimension as per contract : 
2 Rigid section satisfactory : 
3 Flexible section satisfactory : 
4 Connected as per contract drawing : 

Rig floor cement Manifold : 

1 State of maintenance satisfactory : 
2 Same type of valves



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