1. Introduction
Most incidences of stuck pipe are caused by differential-pressure effects. Excessive differential pressures across lower-pressure permeable zones can cause the drillstring to push into the wellbore wall where it becomes stuck. When differential sticking occurs, spotting fluid can sometimes free the drillpipe.
Differential sticking may be identified by the following characteristics:
- Pipe sticks after remaining motionless for a period of time
- Pipe cannot be rotated or moved when circulation is maintained
- The Differential Sticking Tester was designed to determine how likely a given drilling fluid will be to produce a "stuck pipe" situation and how effective a given drilling fluid treatment or application of spotting fluid in any given drilling fluid would be in reducing this tendency. This measurement is called the "Stuck Tendency Coefficient". It takes into account both the stickiness and the cake building capability of the drilling fluid. The "Stuck Tendency Coefficient" is determined by the Timed Filtrate Test.
- The unit can be pressurized by the CO2 regulator assembly or from any nitrogen source. If Nitrogen is to be used, the Differential Sticking Tester must be fitted with a suitable Nitrogen regulator, gauges, relief valve, hose and fittings.
- The measurement can be made using either the flat-faced torque plate or the 12-1/2" (31.75 cm) spherical radius plate which approximates pipe in casing or collars in borehole contact geometry. (Both are provided.) In the event of a "sticky" sample that tends to adhere more to the torque plate than to the filter paper, stainless steel micro-corrugation disks are provided, to help ensure success of the test.
2. Type Specification
| Mode |
Name |
Configuration |
Characteristic |
| NF-2 |
The Differential Sticking Tester |
Pneumatic pressure rod with cylinder assembly |
The adhesion between the adhesive disc and the filter cake depends on the air pressure acting on the pressure cylinder to exert pressure on the adhesive disc |
3. Technical Specification
| No. |
Technical Specification |
| 1 |
Work stress |
3.5MPa |
| 2 |
Maximum pressure of drilling fluid cup |
5MPa |
| 3 |
Diameter of adhesive disc |
φ50.7 mm |
| 4 |
Filter area |
22.6cm2 |
| 5 |
Cup capacity |
240ml |
| 6 |
Air supply |
Nitrogen, carbon dioxide gas (not containing oil, water and other impurities) (oxygen is strictly prohibited), its rated pressure should be greater than 5Mpa |
| 7 |
Net weight / Gross weight |
9.8kg/15.24kg |
| 8 |
Overall dimensions |
500×270×510mm |
| 9 |
Packing size |
560×425×265mm 310×290×285mm |
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