Good morning Ladies and Gentlemen, My name is Charly Hengevoß and I‘m the Drilling Services Technical BD & Sales Advisor from Weatherford Ukraine LLC. I feel privileged to stand here and speak to you. The topic I’ve chosen is: “ How to Improve Overall Recovery with Drilling Services Technology in Mature Reservoirs “. The presentation will show some aspects on improving production by using directional drilling services Weatherford supplies in Ukraine.
The aim of horizontal sections is to increase the active length of the borehole in the production zone. The left plan shows the trajectory of a typical casing exit in 5“ casing with a target zone at 2.300 m TVD and a horizontal section of 200m. The plan on the right shows the same scenario for a new well with a kick of in the 8 ½“ section but with a horiyontal section of 500 m. To reach horizontal different build rates are needed. 20°/30 m for the casing exit versus 5°/30 m for the new well.
For casing exit two different techniques can be applied: Section-milling or Whipstock Section-milled windows take longer than whipstocks. They allow starting higher, thus reducing BUR. On the same well, there could be a difference of 7° at the equivalent “whipstock rathole” depth. When a whipstock is used, undercutting may occur as much as 3 ft above the top. This is important to avoid in case of a water zone . Two- trips whipstock require less rathole than one trip. A long rathole increases BUR needed and implies drilling a tighter curve. Two famous “one trip whipstock” have the first two mills undergauge. Consequently the top mill needs to pass the bottom of the whip-stock. This means loosing as much as 9 ft of TVD. On a semi-straight hole, 9 ft of TVD lost equates to 11° DLS extra (in a 70-ft curve). For a 40-ft curve 9 ft TVD lost equates to 40° DLS extra.
The Weatherford section mill is a hydraulically activated tool used to mill a section of casing or tubing. The section mill is simple in design, is easy to operate, and has an outstanding reputation for performance and durability Milling knifes are dressed with Weatherford’s CustomCut™ tungsten carbide inserts to provide extended footage with maximum penetration rates. The section mill is run in conjunction with a taper mill, which has an integral carbide nozzle threaded in the bottom end. Combined with the integral pack-off system, this configuration allows positive fluid control to the section milling knives. The Weatherford section mill is a product of the company’s MillSmart™ technology – an engineered approach to milling that encompasses a wide range of prooven products, services, and technical resources, developed and refined by the world’s largest and most experienced provider of milling and fishing services.
For whipstocks I‘ll concentrate on hydraulic and mechanical set here.
Features Patented Accuset ™ system inside lead mill provides reliable anchor activation Open-ended BHA allows continuous flow for well control and operation of LWD/MWD before activation of anchor Unique lug technology protects the whipstock during cut-out and accurately directs the mill into the casing wall Shear value for the mill attachment bolt can be adjusted for varying well profiles Multiple methods of whipstock retrieval available Benefits Aggressive lead mill geometry improves rate of penetration and gauge retention Hydraulic activation of the anchor eliminates the need for a false bottom One-trip efficiency; orients, anchors, and mills the window in one run 3° single-angle concave generates a smooth transition from the parent bore into the lateral section Produces full gauge window and rat hole Provides minimal rat hole for tough-to-drill formations Milling BHA and whipstock designed for safe, quick rig floor makeup Applications Where full bore is a requirement after the lateral has been drilled For flow-through capabilities where commingling is a requirement; for example, a level 2 multilateral For severely inclined or deeper wells in which a bridge plug may be more costly and difficult to position Where a casing exit can be created independent of hole azimuth (high and low side exits are possible) For casing exits through multiple strings of casing
Features Unique lug technology protects the whipstock during cut-out and accurately directs the mill into the casing wall Shear value for the mill attachment bolt can be adjusted for varying well profiles Flex-mill tool joint design can incorporate a UBHO sleeve or float body Multiple methods of whipstock retrieval available
Applications Efficient and cost-effective method of sidetracking existing wellbores Where a casing exit can be created independent of hole azimuth (high and low side exits are possible) For casing exits through multiple strings of casing
Benefits Aggressive lead mill geometry improves rate of penetration and gauge retention One-trip efficiency; orients, anchors, and mills the window in one run 1.92° single-angle concave generates a smooth transition from the parent bore into the lateral section Produces full gauge window and rat hole Provides minimal rat hole for tough-to-drill formations Milling BHA and whipstock are designed for safe, quick rig floor makeup
With a Surface Recording Gyro if Borehole Inclination is below 5°. With an MWD System if Borehole Inclination is above 5°. Inside casing the Earth’s magnetic field is disturbed by the metal. So for small inclination where the Earth’s gravity field cannot be used safely to determine the position of the whipstock in relation to the wellbore axis a gyro orientation will be required not only for orienting the whipstock but also for orienting the steerable system.
A whipstock set wrong has a negative impact in the quality of the curve — initial azimuth is important . The milling techniques used can transform a medium radius into a short radius and vice versa. On the average job, this is what happens, with a whipstock: • The first 60 f t are drilled without reliable azimuth data (unless steering gyro is used). • The first valid azimuth appears with 45° of drift at the bit. With section milling (45 ft). • The first 25 ft are drilled without reliable azimuth data. • The next 29 ft (25 ft to 54 ft) are drilled with valid azimuth data.
The biggest difference in azimuth may happen at the start. Using a “steering type gyro” (especially with whipstock) eliminates this risk. Short-radius motors are less powerful but BHAs are limber. Minimum DP should be run above the motor on the first BHA to minimize reactive torque. It is better to drill slower until a clean TF is obtained. A large azimuth error may require a cement plug. Short radius is like drag racing — there is no cure for a bad start.