OS FORM PLUG SYSTEM - Extreme Lost Circulation Solution

 

 

Product Information / Description

The OS FORM PLUG SYSTEM is primarily used as a remedy for EXTREME LOST CIRCULATION.

It is recommended when conventional lost circulation materials have been proved ineffective and the option of using cement is undesirable.

 

It is mixed using standard rig equipment usually in the mud tanks/pits and does not require any specialised equipment.

 

It is pumped (using the mud pumps) as a viscosified fluid to the loss zone (or other placement area) where it sets up as a rigid, yet relatively soft and easily drilled out plug.

 

OS FORM PLUG can be almost completely removed using 15% HCl.

 

OS FORM PLUG consists of a milled borate mineral combined with a unique blend of water-based polymers. It can be adjusted in density by adding barite, or other inert weighting agent, up to 18ppg / 2.16SG and as low as 9.5ppg / 1.14SG.

 

The OS FORM PLUG SYSTEM, with or without weighting agent, can be held as a premix in advance of an anticipated loss circulation requirement and for extended periods of time. In warmer climates, a preservative may be required.

 

The setting mechanism for OS FORM PLUG is a cross-linking process initiated by the addition of OS FORM PLUG A which activates the setting of the system. This should be added just prior to when the material is required to be used.

 

To extend the window of the ‘safe mixing and setting time’ OS FORM PLUG B which is an HT buffer can be added. The quantities are calculated for specific situations after pilot lab testing.

For temperatures greater than 250°F / 120°C and up to 375°F / 190°C the use of an appropriate oxygen scavenger will allow it to remain intact and effective down hole for extended periods of time.

 

OS FORM PLUG can be easily mixed in the mud tanks using standard rig equipment and rig personnel can be quickly trained in its preparation and use.

 

The mixed fluid can be safely pumped through all BHA’s, MWD and LWD tools.

 

All of the chemical components used in the OS FORM PLUG system are ‘green’ and non-hazardous.

 

Application  

The main function of the OS FORM PLUG SYSTEM is to control the losses of mud and wellbore fluids under extreme circumstances. Such losses can be either through large natural or induced fractures and vugs.

Once set it retains a degree of flexibility such that it is deformable under compression yet it can be easily drilled and removed from the wellbore.

 

Due to its adaptable nature other useful applications include:                                 

 

  • Loose formation consolidation (upper hole stone, gravel & sand beds)
  • Cement diversion
  • Non-mechanical removable down hole isolation plug that also prevent gas migration.

 

The ease of ACID REMOVABILTY means it can be used in reservoirs where the use of acid is desirable and/or acceptable.

 

OS Form Plug System Components

Product

Components

Functions

OS FORM PLUG

Milled borate mineral and water based polymers all below 100 microns.

Suspension & chemical cross-linking

OS FORM PLUG A

Specially treated mixture of alkaline oxide and salt.

High ambient temperature cross-link initiator

OS FORM PLUG B

Organic acid in granule  form

Retarder and buffer

 

Mixing Instructions

  1. Ensure that the tanks/pit and mixing lines are cleaned and flushed with drillwater making sure there is nothing left that might affect the pH.
  1. Add the calculated volume of drillwater (or brine) to the pit / tank. The pH is 7 / neutral.
  2. Add the calculated quantity of OS FORM PLUG via the mix hopper as fast as the mixing      equipment will allow – there is no restriction to the speed of additions.
  1. Once all the OS FORM PLUG has been added leave to mix in the normal way for a minimum of 60minutes to ensure the polymers are sufficiently dispersed and hydrated.
  1. Check and adjust the pH to 7-8 using OS FORM PLUG B HT BUFFER after pilot testing.
  1. If required add weighting material in the normal manner.
  1. This mixture can be held as a premix for extended periods or used immediately.
  1. When losses are encountered and the OS FORM PLUG is required, add the calculated quantity of OS FORM PLUG A HT DELAYED ACTIVATOR via the mix hopper as fast as practicable – again there is no restriction to the speed of addition.
  1. PUMP IMMEDIATELY AFTER THE LAST SACK OF ACTIVATOR HAS BEEN ADDED.It must be noted that once the ACTIVATOR has been added it must be used or dumped - UNDER NO CIRCUMSTANCES MUST IT REMAIN IN THE PIT OR PIPES – IT SHOULD BE TREATED LIKE CEMENT AS IT WILL EVENTUALLY SOLIDIFY.
  2. After the activated OS FORM PLUG has been placed in the loss zone wait the agreed setting time before testing the well for losses. If losses are still present a further application may be required.

 

Spacers

The use of spacers is optional depending on rig capability and fluid compatibility.

It has been found that it often has not been necessary to make use of spacers and this indeed can save time when the OS FORM PLUG is needed to be used.

If it is elected to use spacers the simplest is a weighted viscosified water / brine one.

It will also depend on the specific application, eg in the case of lost circulation a spacer or formation stabiliser a spacer ahead  would not normally be necessary, if as a casing / tubing non-metallic isolation barrier / plug it may require a spacer ahead and behind.

It is advisable to evaluate each application according to its own specific set of parameters before making a decision.

 

Mud Compatibility

It has been found that the system can be used with most muds, oil or water based, without detriment to either fluid. More specifically no mud has been found to either ‘flash set’ or inhibit the OS FORM PLUG chemical reaction nor has the OS FORM PLUG been found to adversely affect a mud system – the main effect is physical in that one may dilute the other. Any interphase will either remain downhole or be circulated to the surface where pieces of the set OS FORM PLUG will normally be removed by the shakers. Any fine particulate, polymer or inorganic, may be incorporated in the mud system without any unwanted effect.

 

OS Form Plug Setting Times

Once the ACTIVATOR has been added the OS FORM PLUG WILL set given time. A general guide is shown below:

 

Temperature

Time (Minutes)

50oC

100oC

150oC

60 min

50% set

80% set

+/- 100% set

120 min

90% set

+/- 100% set

 

180 min

+/- 100% set

 

 

It should be noted that the above is just a guide for a basic OS FORM PLUG mixture using OS FORM PLUG A HT DELAYED ACTIVATOR.

It does not take into account the time required to pump the pill to the target zone.

 

Specific fluid densities can be supplied on request.

 

Any formulation required for a specific application should be thoroughly tested under agreed test conditions.

 

It is strongly recommended that OSS be consulted prior to any actual use of this product.

 

 

 

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