Designing a drill string



Designing a drill string

Design a drill string that will pass all the safety factors of the forces of the design. We will start with looking for a well that has 8000 ft as a minimum depth, then calculating the safety factors and limitations of the drill string design. Drilling design will include choosing the drill bit, drill pipe, drill collar, and derrick that will pass all forces affects safely.


Abstract-designing a drill string


The Uinta Basin has turned out to be a standout amongst the most unmistakable mineral asset areas in North America. National consideration is centered around the Basin’s oil and gas potential and also on the enormous oil shale stores. As of late announced appraisals demonstrate that oil saves contained in these stores all through Utah, Colorado and Wyoming in rock holding 25 gallons for each ton or more, contains 700 bbl of oil. By correlation, the aggregate mid-east oil saves, including the rich Kuwait field is assessed to contain just 450 bbls. Tar sand stores are additionally pulling in current consideration. Utah contains 95 percent of the country’s known tar sand holds.

From the roughly 50 known deposits in eastern Utah, an expected 25 billion bbls is contained. Late action and improvement of fluid oil-based commodities in the Altamont-Bluebell territories have been exceptionally productive.

28 miles south of Ouray, Uintah County, Utah state. Uintah County is found near the eastern border of Utah. The Uinta Basin conquers the majority of the county. We can find large oil and gas progress throughout Uintah County.


Discovery Data


The discovery of the Ashely Valley oil field was in 1948, the location of the field is south-east of Vernal, Utah. Uinta Basin Boundary fault located north of the field along the south flank Uinta Mountains.




Oil production from the Weber Sandstone characterizes a combination from source rocks in both the Permian Phosphoria Formation and Cretaceous Mancos Shale. Eolian Pennsylvanian/Permian Weber Sandstone is the main reservoir, it is located in a northwest-southeast-trending, faulted and fractured anticline. Eolian deposits of the Weber Sandstone include dunes, internees, and sand sheets. Throughout the Laramide orogeny the Ashley Valley anticline and further structures created in the area.



Summary and Analysis-designing a drill string


The production test shows the formation produced enough reservoir fluid for good identification. Reservoir pressure drawdown test was enough but shut-in build-ups did not occur for dependable quantitative analysis using the Horner plot. After flow was still in effect on the initial and final Shut-in build-ups to the extent that the plots are considered unreliable for Analysis. The McKinley after flow method was used to determine the reservoir Parameters reported here in. Flow rate gas average flow rate of 142 mcf/d of gas was noticed during this test. Reservoir pressure estimated reservoir pressure or 3844 psi. Permeability the calculated transmissibility factor of 42.47 md.ft/cp. Indicates an average, of Calculations gas gravity 0.70, viscosity 0.022 cp., and gas deviation factor 0.90 and effective permeability to gas 0.0156 md.


The test indicate that the formation shows the characteristics of relatively low permeability effective to the reservoir fluid and shows no well bore damage. The plot of the build-up curve indicates a heterogeneous formation. This may be the result of fractures or stratified layers. A decrease in transmissibility, away from the well bore, is indicated. Based on the indicated decrease, the well would not sustain a flow rate of more than 42.6 mcf/day, under these test conditions.


The size of the field area and the uncommon reservoir rocks need numerous closely spaced wells, using expert drilling and completion technology to produce gas economically. This is applied by hydraulic fracturing technology. Water and chemical mixtures are pumped down the well under high pressures to fracture the sandstone, thus increasing both the porosity and permeability allowing gas to flow to the well bore.



Desgin Designing a drill string


Type Used: hard formation drilling and significantly increase cone durability.

Smith Bits – F35OD

IADC code – 547X

Bit diameter = 8 ¾ in

WOBmax = 50,000 lbs (from Design Specifications)


The depth of the well 8605 ft, and DP OD 5”. Going to the Table I can choose the derrick, that should handle the weight and forces of the rig tools. Thus, from the table provided, the derrick selected was the API Number 18 A, Height 136 ft. This API derrick size takes 5” DP and capable to reach a depth of 9,800 ft, which almost close to our depth.










Design Data


Depth (D) 8605 ft
Density of Steel (ρsteel) 65.50 ppg
Density of Mud (ρmud) 9.10 ppg
Weight on Bit (WOB) 50000 lbf
Length of Drill String (LDS) 8605 ft
Margin of Pull (MOP) 100000 lbf
Safety Factor (Nc) 1.20
Drill Collar 6.00‘’ O.D., 1.50’’ I.D., 90 lbf/ft
Collapse Resistance (Ptc) 12010 psi
Drill Pipe Grade X 5.00’’ O.D., 4.28’’ I.D., 19.50 lbf/ft
Drill Bit 8 3/4’’ Critical Speed: 50 – 250 rpm
Average Yield Strength Grade E Drill Pipe 95000 psi
Length of Drill Pipe Joint (lDP) 30 ft



















Conclusion and Results

After studying the forces on our design using the class notice, it is obvious that the design meets all the safety factors and factory safety factor values required to continue the operation to the desired depth without failing.


DP Collapse Rating, psi 12010
DP Burst Rating, psi 12040
DP Tension Rating, lbs. 501000

 Designing a drill string

Furthermore, the Derrick efficiency calculated are around 89.24 %. Finally, selecting Drill Pipe Grade X 5.00’’ O.D., 4.28’’ I.D., 19.50 lbf/ft, Smith drill Bit 8 ¾ in, the derrick size API Number 18 A, Height 136 ft, and Drill Collar 6.00‘’ O.D., 1.50’’ I.D., 90 lbf/ft, will allow us to drill to the desired depth 8605 ft safely and efficiently























Work Cited


  • Class Notes for Drilling Engineering