Description
Mechanical Upward & Downward Jarring Without Hydraulic Delay
The QJZ Mechanical Drilling Jar is a fully mechanical, double-acting downhole jarring tool designed to remain in the drill string during normal drilling and provide upward or downward impact when a stuck-string condition occurs. Mechanical control and release components respond to axial loading from surface, giving drilling teams a direct jarring option without relying on a hydraulic time-delay mechanism.
Mechanical Activation
Up & Down Jarring
NC / REG Connections
Quick Answer: What Is the QJZ Mechanical Drilling Jar?
The QJZ Mechanical Drilling Jar is a double-acting drilling jar that uses a mechanical locking and release system rather than a hydraulic delay section. It is run as part of the drill string and remains available during drilling. If the string becomes stuck, controlled surface overpull is used for upward jarring, while controlled compression is used for downward jarring. The QJZ series is available in six models from 121 mm to 229 mm OD with NC and REG connection options.
Product Highlights
Fully Mechanical Release
Mechanical control and release components activate through axial loading, without depending on a hydraulic time-delay mechanism.
Double-Acting Jarring
Provides both upward and downward impact capability so the operator can select the required jarring direction for the stuck condition.
Drill-String Integrated
The jar remains part of the drill string during normal operation and can be activated when a jarring response is required.
Defined Up & Down Stroke
Each model has specified upward and downward stroke values to support engineering selection around the planned BHA.
High Axial Load Capacity
The QJZ range provides maximum tensile ratings from 1,400 kN to 3,000 kN, depending on model.
NC & REG Tool-Joint Options
Connections range from NC38 to 7 5/8 REG across the supplied model series for drill-string integration.
How the QJZ Mechanical Drilling Jar Works
The QJZ jar uses a mechanical control and release arrangement built around the mandrel, control sleeves, spline body and compression components shown in the tool structure. During normal drilling, the assembly remains in its running condition as part of the drill string. When jarring is required, axial load is applied from surface until the mechanical release sequence is completed and the moving components accelerate into the impact position.
1. Running Condition
The mechanical jar is run in the drill string as a normal downhole component until a stuck-string condition requires jarring.
2. Upward Jarring
Surface overpull loads the jar in tension. When the mechanical release condition is reached, stored axial energy in the drill string drives the upward impact stroke.
3. Downward Jarring
Controlled compression loads the jar in the opposite direction. Mechanical release allows the internal moving section to travel through the downward stroke and generate impact in the required direction.
Where a Mechanical Drilling Jar Fits in the BHA
Provides an available impact mechanism when axial loading alone cannot release a stuck drill-string or BHA condition.
A suitable option when the drilling program calls for a fully mechanical release principle rather than hydraulic delay activation.
Double-acting operation allows the drilling team to apply impact in either direction according to the stuck condition.
Model selection is matched to OD/ID, connection, tensile load, torque, jarring force and stroke requirements.
QJZ Mechanical Drilling Jar Technical Specifications
The QJZ series covers six tool sizes. Select the model by matching the BHA envelope, connection, required upward/downward jarring force, maximum tensile load, working torque and stroke. The effective pump area listed in the source datasheet is included for engineering review of circulating conditions.
| Model | OD (in / mm) | ID (in / mm) | Up Stroke (in / mm) | Down Stroke (in / mm) | Max. Up Jarring Force (kN) | Max. Down Jarring Force (kN) | Max. Tensile Load (kN) | Max. Working Torque (kN·m) | Effective Pump Area (cm²) | Connection |
|---|---|---|---|---|---|---|---|---|---|---|
| QJZ121 | 4 3/4 / 121 | 2 / 51 | 7 7/8 / 200 | 7 7/8 / 200 | 400 | 250 | 1400 | 10 | 70.8 | NC38 |
| QJZ159 | 6 1/4 / 159 | 2 1/4 / 57 | 5 5/8 / 142 | 6 3/4 / 172 | 600 | 350 | 2200 | 15 | 115.7 | NC46 |
| QJZ165 | 6 1/2 / 165 | 2 1/4 / 57 | 5 5/8 / 142 | 6 3/4 / 172 | 620 | 350 | 2200 | 15 | 115.7 | NC50 |
| QJZ178 | 7 / 178 | 2 1/4 / 57 | 5 7/8 / 149 | 6 5/8 / 168 | 700 | 420 | 2200 | 15 | 132.7 | NC50 |
| QJZ203 | 8 / 203 | 2 13/16 / 71.4 | 5 13/16 / 145 | 7 / 178 | 800 | 450 | 2500 | 20 | 174.3 | 6 5/8 REG |
| QJZ229 | 9 / 229 | 3 / 76.2 | 8 / 203 | 8 / 203 | 1000 | 500 | 3000 | 25 | 240.4 | 7 5/8 REG |
Model selection must be based on the complete drill-string and BHA operating envelope. Maximum values in the table are tool ratings from the supplied product datasheet, not recommended routine operating loads.
How to Select the Right QJZ Model
1. Match Tool OD & ID
Start with the available BHA envelope and required internal flow path. QJZ tool OD ranges from 121 mm to 229 mm and ID from 51 mm to 76.2 mm.
2. Confirm Connection
Match the jar to adjacent drill-string components using the specified NC38, NC46, NC50, 6 5/8 REG or 7 5/8 REG connection.
3. Check Axial & Torsional Capacity
Compare the planned drill-string loads with the model’s maximum tensile load and maximum working torque before selecting the jar.
4. Define Jarring Direction & Force
Review both upward and downward jarring requirements rather than selecting only by tool diameter.
5. Review Stroke
Upward and downward stroke varies by model. Include stroke in the BHA and operating review when the available movement envelope is limited.
6. Include Circulating Conditions
The datasheet provides effective pump area for each model. Include circulating pressure and hydraulic force effects in the complete operational load review.
Mechanical Drilling Jar vs. Hydraulic Drilling Jar
QJZ is intended for buyers who specifically want a mechanical release principle. For projects that require hydraulic delay release, the QY Full Hydraulic Drilling Jar is the corresponding hydraulic option.
| Selection Factor | QJZ Mechanical Jar | QY Hydraulic Jar |
|---|---|---|
| Release Principle | Mechanical locking / release mechanism | Hydraulic delay-release mechanism |
| Jarring Direction | Upward and downward | Upward and downward |
| Delay Section | No hydraulic time-delay section | Hydraulic delay before release |
| Primary Buying Question | Mechanical activation, load rating, torque, stroke and connection | Hydraulic release force, temperature, load rating and connection |
Key QJZ Structure Elements
The supplied QJZ structure drawing identifies the main mechanical sections used to transmit torque, control axial movement and generate the jarring stroke.
Top Sub & Mandrel
Connect the jar into the drill string and transmit axial load through the tool.
Upper / Lower Control Sleeves
Form part of the mechanical control sequence governing tool movement and release.
Spline Body
Supports torque transmission while allowing the axial movement required for the jarring cycle.
Compression / Moving Components
Control relative axial travel during loading, release and reset of the double-acting jar.
Information Required for Quotation
For a model-based quotation, send the drilling and BHA data needed to match the mechanical jar to the actual operating envelope.
Related Drill-String Equipment
Drilling Jar OverviewReview the broader drilling-jar product range and the main hydraulic and mechanical options.
Drill CollarCoordinate jar connection and BHA load capacity with surrounding heavy drill-string components.
Drilling StabilizerReview stabilizer placement and BHA geometry together with the mechanical jar configuration.
FAQ: Mechanical Drilling Jar Selection & Procurement
How is the QJZ mechanical drilling jar different from a hydraulic drilling jar?
QJZ uses a mechanical control and release system. A hydraulic jar such as the QY series uses a hydraulic delay-release mechanism. Both can provide upward and downward jarring, but the activation principle and the selection data required for the two tool types are different.
Can the QJZ jar remain in the drill string during normal drilling?
Yes. The supplied product description identifies the QJZ as a drilling jar that remains part of the drill string and can be used when jarring becomes necessary.
How are upward and downward jarring initiated?
Upward jarring is initiated by controlled surface overpull; downward jarring is initiated by controlled compression. The mechanical release sequence then allows the internal moving section to complete the required impact stroke.
Which QJZ model should I select?
Select by tool OD/ID, connection, required upward and downward jarring force, maximum tensile load, working torque, stroke and circulating condition. The jar must be evaluated with the complete BHA rather than by OD alone.
Why is the effective pump area included in the specification table?
The effective pump area is relevant when circulation pressure creates an additional axial hydraulic force across the tool. It should be included in the operational load calculation together with surface-applied tension or compression.
What connection options are available in the QJZ series?
The supplied series includes NC38, NC46, NC50, 6 5/8 REG and 7 5/8 REG connections, depending on model.
Should maximum tensile load be treated as the planned operating load?
No. The maximum tensile value is a tool rating from the product datasheet. Routine operating limits and jarring procedures must be established from the complete drill-string design, connection limits and approved operating program.
What information gives the fastest mechanical drilling jar quotation?
Send required OD/ID, connection, hole size or BHA envelope, upward/downward jarring requirement, maximum expected tensile load, working torque, circulating pressure condition and quantity.
Select the QJZ Jar by Load, Stroke & Connection — Not by Diameter Alone
Send your BHA envelope, connection, expected tensile and torque load, required upward/downward jarring force and circulating condition. Shangshanpetro can prepare a model-based quotation for the QJZ Mechanical Drilling Jar.
