Directional Drilling & Fishing. Directional Drilling. Directional Drilling: deviation from drilling a straight hole. Drilled straight to a predetermined depth, and then gradually curved. Typical curvature: 2-3 degrees per 100’ of well depth
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Directional Drilling • Directional Drilling: deviation from drilling a straight hole. • Drilled straight to a predetermined depth, and then gradually curved. • Typical curvature: 2-3 degrees per 100’ of well depth • Drill stem can handle this low angle curvature enough to eventually run horizontal.
Directional Drilling • Uses • Offshore • Development Drilling on Land • Other (well control) • Tools and Techniques • Drill Pipe • Bent Sub and Downhole Motor • Orienting the Hole
Directional Drilling (Uses) • Offshore: • One of the most important uses • Capability to drill multiple wells from one location • Due to huge expense of constructing a platform, this enables operators to capitalize on a single investment for multiple producing wells • Example: Gullfaks C platform in the North Sea • Weighs 1.5 million tons • Covers 4 acres • Cost the US 2 billion to build
Directional Drilling (Uses) Gullfaks C Platform Typical North Sea Day
Drilling Offshore From Land Rig Location on Land Pay Zones Offshore This method is much cheaper and safer than offshore drilling.
Development Drilling on Land • Directional drilling on land has several uses: • Avoiding Fault Lines • Can cause problems in the hole • Rig Location • Rivers, Hills, Mountains and other obstructions • Well orientation in the pay zone • Operators have increased production by up to 10x due to horizontal well orientation. • Drilling in shale formations. Exposes more of the fractures to the wellbore increasing production. (Recent success and industry highlight)
Other Uses • Exploration: • Directional allows for deflecting off original “dry” holes to intersect possible pay zones. • Sidetracking: • Divert around a fish (object lodged in the borehole) • Well Control: • Killing “Wild Wells” • Relief Well is drilled directionally to intercept the blown out well in order to kill the well by pumping mud down hole.
Tools and Techniques • Drill Pipe: • Place drill collars at the lower portion of the vertical section of the drill string and above the lower section of the drill pipe. • Manufacturers have engineered new types of drill pipe especially for horizontal drilling. • Bent Sub: • Short piece of pipe threaded on both sides and bent in the middle • Typically the bend ranges from 1-3 degrees off vertical • Placed in the drill string between the bottom most drill collar and the down hole motor. • Bent Sub deflects the down hole motor and bit off vertical
Tools and Techniques • DownHole Motor: • Only Rotates the drill bit, not the drill string • Shaped like a piece of pipe, can have turbine blades or a spiral steel shaft that rotates when the drilling mud passes through it. • Since the bit is attached to the shaft it rotates when the shaft turns.
Directional Drilling Animation • http://www.youtube.com/watch?v=t_AL7rNmWUA • http://www.youtube.com/watch?v=O0kmskvJFt0&NR=1
Orienting the Hole • Inclinometer: • Directional instrument that uses magnetic or gyroscopic compass and inclinometer to measure the angle of the hole. • Steering Tool: • Sends directional information up the hole through a wire line to a monitor on the rig floor • Mud Pulse Generator: • A wireless self contained instrument that transmits sonic signals up the hole, through the drilling fluid in the drill stem, to a readout device on the surface. • MWD: • (Measurement While Drilling) uses the Mud Pulse Generator and allows the driller to get information from the bottom of the hole without stopping drilling at all. Used for straight and directional control measurement.
Fishing • Fishing: • The term used for retrieving any object from the wellbore: • Examples: • Drill Stem (Part or Whole) when it gets stuck • Smaller pieces of equipment (Also Known as “Junk”) • Bit cones • Hand Tools • Pieces of Steel
Fishing • Causes of Stuck Pipe: • Hole Collapses around the pipe • Pipe gets stuck in a dogleg or “key seat” • Pressure can hold the drill collars so securely to the wall that no amount of pulling can free the pipe.
Fishing • Hole Collapses: • Typical causes: • Interstitial Salt Water (Water contained in the pores of formation rock) can attract the water in the drilling mud. • If the formation is shale, the water in the mud has a tendency to transfer to the shale causing it to slough off into the hole. • Hole eventually fills in and causes the BHA to become stuck.
Fishing • Key Seat: • Caused by a dogleg (Crooked section of hole) • Drill pipe leans against the side of the dogleg, and as the pipe rotates it digs out a new smaller hole in the side of the main borehole. • When the drill stem is pulled from the hole, the tool joint being wider becomes logged in to the key seat.
Fishing • Pressure: • Mud weight that is to heavy for the formation causes a heavy wall cake • When the drill string is not rotating (ie. Making a connection or tripping) it can rest on the narrowed wall. • The pressure from the mud and contact with the wall causes the drill string to become stuck • Typically it can be freed by spotting oil/lubricant in the stuck area and then jarring on the drill string. • Drilling Jar or Bumper Sub: Special tool that provides heavy blows to the drill string upward or downward. • http://www.youtube.com/watch?v=v2jvHD897Ss&feature=related
Fishing • Free point Indicator: • Used to locate the stuck portion of pipe • Indicator induces a magnetic field in the pipe and sends a signal to a meter on the surface. • When the driller picks up on the drill string it stretches in places where it is not stuck, this causes a strong signal reading (needle moves a lot) • When the driller picks up in the drill string and it does not stretch this is indicated by little or no movement on the drill string, this is your stuck point. • The depth is then noted.
Fishing • String Shot: • Long string like explosive charge that is usually run below the freepoint indicator. • The string is set off helping to loosen the threads of the pipe • Driller turns the rotary table to the left to back off the pipe. • Washover Pipe / Washpipe: • Crew trips in with a special tool while circulating and rotating. Tool contains a cutter called a rotary shoe that cuts away shale or wall cake while latching on to the “fish” with a backoff connector inside the wash pipe.
Fishing • Twist Offs: • When a portion of the drill string twists off. • Typically due to fatigue or damage the pipe literally breaks in two. • Typically not complicated • Tools used: • Overshot: Goes over the fish and grips it firmly using a grapple • Spear: Goes inside the fish and grips it (used for collars)
Questions • What is directional drilling? • Why is directional drilling important to offshore operations? • What are the advantages of drilling onshore? • Why is horizontal drilling so popular and a key in the industry’s success in 2013? • How is a horizontal well used to “Kill” a blow-out? • What is “fishing” • What is a free point indicator used for? How does it work? • What is the difference between an overshot and a spear?