Product Description
OSTOP® lost circulation material (LCM) is a highly effective, high-fluid-loss industry standard product containing diatomaceous earth blend, specially designed to cure for severe or total loss. It has been used over 1000+ wells with highest success rate in the industry. It is a fast acting and extremely cost-effective solution to lost circulation in many types of downhole conditions including fractures, vugular formations and weak channels. As a pre-mixed and one single sack solution, OSTOP® eliminates the guesswork associated with a response to severe loss. It is mixed in drill water or oil and is compatible in all types of fluid systems. A solid plug is formed in the thief formation when water or oil is squeezed from the slurry. OSTOP® can provide a complete seal in one application which makes it the first choice to cure losses from partial to severe lost circulation scenarios.
Applications/Functions
- Cures partial to wide ranging severe loss situations
- Open hole remedial and/or preventive lost circulation squeeze
- Improves casing shoe integrity
Advantages
- A single sack solution to eliminate the guesswork associated with a response to severe loss
- Can be mixed and maintained on the rig for immediate application upon lost circulation
- Mixed easily in drill- water, weight up slurry in excess of 2.35 SG (19.6ppg)
- No activators, accelerators, or retarders required
- Eliminates need for multiple LCM products thus saves rig space and minimizes waste
- Applications in all drilling fluid systems (water-, oil-, or synthetic-based)
- No risks of cementing up the drill pipe
- No Pre-Spots or Spacers required
- Proven high success ratio in the industry and used over 1000+ wells worldwide
- Extremely cost-effective material and procedure for remedying lost circulation
Typical Properties
- Appearance: Mixer of white and gray particles with black and tan granules and fibers
- Specific gravity: 1.8
Recommended Treatment
| LCM Pill Formulation for 50 BBL (8m3) |
| MW, PPG |
MW, SG |
Water, m3 |
OSTOP®, SACK |
Barite, MT |
|
| 9 |
1.08 |
7.5 |
62.5 |
0.00 |
|
| 10 |
1.20 |
7.0 |
62.5 |
1.36 |
|
| 11 |
1.32 |
7.0 |
59 |
2.72 |
|
| 12 |
1.44 |
6.5 |
52.5 |
4.08 |
|
| 13 |
1.56 |
6.5 |
49 |
5.22 |
|
| 14 |
1.68 |
6.0 |
44 |
6.58 |
|
| 15 |
1.80 |
5.5 |
39 |
7.94 |
|
| 16 |
1.92 |
5.5 |
35 |
9.07 |
|
| 17 |
2.04 |
5.5 |
31.5 |
10.44 |
|
| 18 |
2.16 |
5.0 |
27.5 |
11.80 |
|
| 19 |
2.28 |
4.5 |
21.5 |
13.16 |
|
Package
Mixing Procedure
The High Fluid Loss Squeeze differs from many loss circulations remedies. When squeezing into a loss zone, the liquid phase (water) is filtered out of the slurry. A firm, dense plug remains within the fracture or permeable zone rather than at or near the face of the wellbore. This promotes "fracture tip seal-off" and prevents the propagation of the fracture. It also minimizes the possibility of the seal being removed during drilling operations and/or repeated remedial loss treatments. Water based high filtrate pills are recommended in well bores where water and oil / synthetic based fluids are used.
- Mix twice the open hole volume or a minimum of 100 bbls (16 m3) of slurry for longer open hole intervals. Ideally, enough slurry should be available to cover all potential loss zones, as well as enough excess volume available for squeezing operations.
- Begin with approximately 80% of prescribed volume of water (see mixing table). Add OSTOP®, Barite, and then the remainder of the water.
- If spotting a weighted slurry, it should have the same density as the drilling fluid in use.
Pumping Procedure
- Run the bottom of drill pipe or bit to a depth that will allow an equivalent of the calculated open-hole volume to remain inside the casing above the casing shoe. To prevent stuck pipe, do not run the pipe into or below the loss zone.
- Pump the slurry at >5 bpm (600 lpm) until it reaches the end of the pipe. Pump the slurry at a rate to clear the drill pipe within 30 minutes. Before beginning the hesitation squeeze, check the annulus. If no fluid can be seen, use the fill-up line and fill the hole.
- Close annular BOP, and pump slurry at 1.25 bpm (150 lpm). This will direct the slurry downhole to the point of loss. Pump the full open hole volume, plus an additional 20-25 bbl (3-4 m, leaving remaining slurry in the drillpipe for squeeze operation.
- Begin pumping at 0.25-0.5 bpm (40 lpm to 80 lpm). When a pressure of 50 psi (3 bar) is obtained, discontinue pumping for 10-15 minutes. Repeat this procedure until 50 psi (3 bar) can be maintained, then attempt progressively higher pressures in 40-50 psi (2-3 bar) increments. With this hesitation squeeze method, there will be a pressure bleed off each time the pump is stopped. However, with each successive squeeze, the pressure should stabilize at a higher level.
- A 200-600 psi (15-40 bar) squeeze is generally considered to be very good, but it may be advisable to squeeze to a higher equivalent mud weight if it is known that a higher fluid density will be needed in this hole interval. When maximum holding pressure is obtained, shut down for two to four hours.
- Bleed the pressure from the annulus slowly, and then circulate the remaining LCM pill out of the hole.
- Run the drill pipe back into the hole slowly, monitoring the weight indicator and checking for bridges. Wash to bottom, drilling any LCM plug if encountered. Any remaining LCM may be retained in the drilling fluid.
NOTES
- There are two key factors to obtaining a best possible chance for a successful LCM Squeeze:
- Slurry with an extremely high solids content and high fluid loss must be prepared.
- It must be placed at the proper location in the wellbore so that it can seal the loss zone.
- Do not hurry to build squeeze pressure. Patience and time are necessary to obtain a successful squeeze.
- Do not mix weighted slurry too far in advance of using it. All weighted fluids are subject to barite settling with time.
- Use a low-pressure gauge to accurately measure squeeze pressure. If possible, rig-up equipment so that drill pipe and casing pressures can be monitored easily and precisely.
- If slurry is to be placed through the bit, install a drill pipe screen or choke nipple. The choke nipple should be smaller than the bit nozzle size. This will prevent plugging of the bit, and foreign objects can be easily removed at surface to avoid disrupting operations.
- No special equipment is needed to pump low weight (<12ppg or <1.44SG) slurries. The slurry can be mixed in a clean, uncontaminated mud pit and pumped with rig pumps. The operators may consider using a cement company blender and pump unit to place weighted slurries of over 12ppg (1.44SG). This gives better control of squeeze pressure and avoids contamination.
- Attempt to accurately determine location of loss zone, to increase the chances for obtaining a successful squeeze. (Temperature log and/or MWD)
- An onsite test to ensure high fluid loss prior to pumping may be done with an API filter press pressured to 6.8 bar. It should lose all of its water in approximately 2 minutes.
- Always have sufficient quantity of material on location for additional squeeze procedures.
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