Downhole Equipment

One load path, four sub-Categories

The drill string carries hanging weight in tension, transmits rotary torque, holds internal mud pressure and bends through every dogleg while it turns. Each rotation in a curved hole is one fatigue cycle. The weakest element sets the rating of the whole string, and in used equipment that is nearly always a connection, an upset runout or the slip area of the tube.

Start with pipe and collars when you are building or topping up a full string. Go to the tool pages when a single BHA component or crossover is missing.

Standards that govern the group

• API Spec 5DP covers new drill pipe in grades E75, X95, G105 and S135, at product specification levels PSL-1 to PSL-3. Higher levels add toughness and testing requirements.
• API Spec 5CT covers casing and tubing, which is the basis for tubing work strings.
• API Spec 7-1 covers rotary drill stem elements. Its 2023 second edition includes kellys, kelly valves, subs, steel and non-magnetic drill collars, heavy-weight drill pipe and stabilizers.
• API Spec 7-2 covers threading and gauging of rotary shouldered connections.
• API RP 7G gives design and operating limits, including tension and torsion ratings for premium and Class 2 pipe and make-up torque for connections.
• API RP 7G-2 sets out inspection and classification of used drill stem elements.
• DS-1 and NS-2 are owner-specified inspection standards. DS-1 came from T H Hill Associates, which Bureau Veritas bought in 2012, and Bureau Veritas now develops it. Many contracts call for one of them in place of RP 7G-2.

An API monogram records how a part was made. It says nothing about today's wall, threads or fatigue, so a recent inspection report outweighs it on a used lot.

Sour service across the string

NACE MR0175 / ISO 15156 governs materials exposed to hydrogen sulfide. It notes that drill string parts often need strengths too high to meet its hardness limits, and that the main defence against sulfide stress cracking while drilling is control of the drilling fluid. For a sour well, plan on sour-service drill pipe grades from the mill, H2S scavengers and pH control in the mud, and treat a standard S135 string as unsuitable.

Inspection categories decide what a report is worth

A report is only as useful as the scope it covers. DS-1 groups drill pipe inspection into Categories 1 to 5. Category 1 is little more than a visual check and OD gauging. Category 3 matches the standard rack inspection most fleets run, with ultrasonic wall checks and full-length electromagnetic inspection (EMI) of the tube. Categories 4 and 5 add magnetic particle or ultrasonic inspection of the slip and upset areas and fuller dimensional and black-light checks of every connection. Pick the category from the consequence of a failure in your well, then check the report actually ran it.

For BHA tools and collars, the connections get wet fluorescent magnetic particle inspection on steel and liquid penetrant on non-magnetic material. Moving tools such as jars also need the maker's strip-down and test.

Integration questions that cut across the group

• Connection chain. Every change of connection between pipe, heavy-weight, collars, tools and bit needs a crossover, and each crossover has its own make-up torque and fatigue limit.
• Handling equipment. Tool joint OD and the 18 degree elevator shoulder must suit your elevators, iron roughneck and pipe handler. Collars without lift recesses need lift subs.
• Bore. The minimum ID along the string decides whether drop balls, darts and wireline survey tools can pass.
• Hardbanding. Casing-friendly hardbanding protects your casing as well as the tool joint.

Used, unused surplus or new

Unused surplus from a cancelled program usually comes with mill certificates and full wall, which makes it close to new once you confirm storage condition. Premium used pipe and re-inspected collars suit most development wells with a known load case. For deep, high-pressure or extended-reach wells, insist on a fresh high-category inspection before you commit. Naventr can arrange an independent inspection on request and answer questions from the Seller's records.