Petroleum engineering (drilling) project 2

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Class6_Trends_StuckPipe.pdf

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Drilling Engineering

Class 6

Drilling Trends

• The driller communicates with the hole through monitoring trends

• You will not see trends unless you write the numbers and make a log

• Establish a base line for trends in a clean wellbore

• Watch the trends periodically and when you see changes, figure out why.

• Monitoring trends and reacting to unusual changes will prevent unscheduled events

Hole Trends

• Pump Pressure and Pump Rate (Strokes)

• This is the most important trend to watch

• Driller periodically takes a slow pump rate pressure

• Factors that influence Pressure/Stroke relationship:

• Hole Depth, Hole/Pipe Geometry, Surface Plumbing, Mud Properties, Downhole Tools, Pump Characteristics

• 𝑃2 = 𝑃1 𝑆𝑃𝑀2

𝑆𝑃𝑀1

Hole Trends

• Pressure/Stroke Relationship

• Any sudden change in pressure while drilling could indicate one or more of the following:

• Hole Restriction

• Hole Loading with cuttings- Dirty wellbore

• Kick taking place

• Drill String Washout

• Loss Circulation to formation

Hole Trends

• Example: Pressure/Stroke Relationship

• Driller has the following properties while drilling:

• Stand Pipe Pressure = 3,000psi

• Pumps set at 100 spm

• The driller then observes the following change:

• The SPP suddenly drops 200psi to 2800psi

• He double checks the pumps and they are still set at 100 spm

• What is happening?

• What should you tell your driller to do?

Hole Trends

• Example: Pressure/Stroke Relationship

• Could mean

• Drill String Washout

• Lost Nozzle in the bit

• Taking a kick

• What should the driller do?

• Stop the pumps and check if the well is flowing

• Have the derrickman check the pumps for leaks (blown seals/gaskets)

• Running a downhole motor? Does the directional driller still see differential pressure? Can he downlink a survey?

• If SPP is still low, begin to TOH and check for washout in string 6

Hole Trends

• Drag Trends

• Pick up/Slack off weights (PU/SO)

• The driller must establish the drag trend in a clean hole

• By trending the PU/SO weights a drag trend can be formed

• This can tell you when it is time to stop drilling and circulate to clean the wellbore

• This data is imported into Torque and Drag models to help determine friction factors

Hole Trends

• Torque Trend • This is a measurement of rotational torque in the drill string

• Torque is influenced by the following: • The drill string making contact with the wall of the wellbore

• Bit penetrating the rock

• Doglegs and well geometry

• Drilling fluid lubricity

• Amount of cutting beds

• Gradual increase in TQ • Possibly cuttings build up. Circulate a bottoms up and see if it

decreases

• Sudden increase in TQ • Possible formation change

• Downhole Tool Failure

• Bit under gauge: Motor or stabilizer entering the under gauged hole 8

Hole Trends

• Rate of Penetration ROP

1. In non permeable zones, like shale, the ROP is directly proportional to the porosity of that rock

2. In permeable zones, ROP is mainly effected by mud properties

3. The plot of ROP will appear very similar to a neutron porosity plot on the same scale

• Bit wear

• As the bit wears, the ROP will slowly decrease over the footage drilled. At some point when it is uneconomical to continue drilling with that bit, a bit trip is necessary.

Hole Trends

• Tripping Trends are used for T&D models to determine FF

• Tripping out of the hole TOH

• You will see drag trends as the BHA is pulled through doglegs, cutting beds, and other tight spots

• It may be a good idea to ream around these spots until the drag decreases. This will help prevent issues when running casing

• Is the hole taking the proper amount of fluid to fill?

• Tripping in the hole TIH

• Same drag trends as above

• Same to watch mud volume as you fill

• Once on bottom and circulate the mud, do you see gas cut mud? Should the MW or YP be adjusted? 10

Hole Trends

• Cuttings Trends

• The cuttings over the shakers can tell you the most about what is going on downhole

• The amount, size, and shape of the cuttings

• The formation lithology being drilled can be identified

• Background gas coming to surface

Torque & Drag Modeling

• T&D modeling is an essential step in planning for horizontal wells.

• Optimum drilling parameters can be estimated and simulations can be evaluated to predict if/when drill pipe buckling and/or failure may occur • Sinusoidal Buckling

• Helical Buckling

• Tensional Yield Failure

• Torsional Yield Failure • Occasional Sinusoidal Buckling is

a common phenomenon while drilling Horizontal wells.

• Helical Buckling is dangerous and will cause fatigue and failure much quicker

• https://www.youtube.com/w atch?v=4gTaEyx8aTE

T&D Example

Drilling Production Curve/Lateral

Planned Drilling T&D Model w/ sensitivity FF

Planned Casing Run with sensitivity FF

T&D Model with PU/SO data while drilling -What open hole friction factor is this well trending?

T&D Model with TOH data after well was TD’d -Now what open hole friction factor can be interpreted?

Running Production Casing Plan -How much should the driller see on the weight indicator at TD while running casing?

Stuck Pipe

• Causes of Stuck Pipe

• Differentially Sticking

• Requirements: Permeable formation, High Differential pressure, Wall contact by the drill string, lack of pipe movement, mud properties to form a mud cake

• Formation Related Stuck Pipe

• Sloughing shales, Fractured shales, Clay/Shale swelling,Salts

• Mechanically Related Stuck Pipe

• Doglegs, Keyseats

• Cutting beds

• Wash out sections

• Junk downhole

Freeing Stuck Pipe

• Drill String Data (in order from surface to TD)

• 7000’ DP, 5”, 19.5ppf, Grade S-135, XH

• 5000’ DP, 5”, 19.5ppf, Grade E-75, XH

• 720’ DC, 6-1/2” X 3-13/16”

• Mud

• MW= 14ppg;

• 𝐵𝐹 = 65.44−14

65.44 = 0.786

Freeing Stuck Pipe

1. Calculate air weight of the string

• Adjusted weights from charts

• DP, S-135: 22.60#/ft * 7000ft = 158,200

• DP, E-75: 20.89#/ft * 5000ft = 104,450

• DC: 91#/ft * 720ft = 63,700

𝑊𝑇𝑎𝑖𝑟 = 326,350 𝑙𝑏𝑠

Freeing Stuck Pipe

2. Calculate weight indicator weight if the blocks weigh 100,000 lbs

𝑊𝑇𝑊𝐼 = 𝑊𝑇𝑎𝑖𝑟 ∗ 𝐵𝐹 + 𝐻𝐿

𝑊𝑇𝑊𝐼 = 326,350 ∗ 0.786 + 100,000 = 356,511 𝑙𝑏𝑠

Summary:

𝑊𝑇𝑎𝑖𝑟 = 326,350 𝑙𝑏𝑠 𝑊𝑇𝑊𝐼 = 356,511 𝑙𝑏𝑠

Freeing Stuck Pipe

3. Calculate volume of mud required to pull out of hole

• You can look up the pipe displacement in charts for each section of pipe, or you can estimate by using the following:

• Steel weighs 2,748 lbs/bbl

𝑉𝑜𝑙𝑡𝑟𝑖𝑝 = ൗ 𝑊𝑇𝑎𝑖𝑟

2748

𝑉𝑜𝑙𝑡𝑟𝑖𝑝 = 326,350

2748 = 118.8 𝑏𝑏𝑙𝑠

Freeing Stuck Pipe

4. Calculate the estimated stuck point ESP

1. Pull ½ of MOP = 50,000 lbs

2. Mark the pipe

3. Pull an additional 40,000 lbs

4. Measure the stretch, e in inches; use 37.5” for class example

5. Repeat to verify

• One size drill pipe

𝐸𝑆𝑃 = 735,294 ∗ 𝑒 ∗ 𝑊𝑝𝑒

𝑃 ‘e’ is the stretch in inches, P is the differential pull in lbs

Obtain Plain End Weight from Table Q: New Drill Pipe Dimensional Data

Plain End Weight: 𝑊𝑝𝑒 = 𝐷𝑃𝑜𝑑 2 − 𝐷𝑃𝑖𝑑2 ∗ 0.7854 ∗ 3.4

Freeing Stuck Pipe

𝐸𝑆𝑃 = 735,294 ∗ 𝑒 ∗ 𝑊𝑝𝑒

𝑃

𝐸𝑆𝑃 = 735,294 ∗ 37.5 ∗ 17.93

40,000 = 12,360 𝑓𝑡

The estimated stuck point is in the drill collars

Summary: 𝑊𝑇𝑎𝑖𝑟 = 326,350 𝑙𝑏𝑠 𝑊𝑇𝑊𝐼 = 356,511 𝑙𝑏𝑠 𝑉𝑜𝑙𝑡𝑟𝑖𝑝 = 118.8 𝑏𝑏𝑙𝑠

𝐸𝑆𝑃 = 12,360 𝑓𝑡 25

Freeing Stuck Pipe

• If you cannot get circulation or rotation or pull the string free, we can either:

• Mechanical Backoff: recover partial of the string with a mechanical back off, then fish the remaining string.

• String Shot: try to recover as much of the string as possible, then either fish the remaining pipe or place a cement plug and go around the fish.

• Wireline free point tools can be used to see torque, locate tool joints, and find stuck point in a directional well

• Be sure not to back off near the casing shoe

Freeing Stuck Pipe

5. Calculate the back off weight BOW to make a mechanical back off at 3,000 ft (note the grade of DP at 3,000ft).

𝐵𝑂𝑊𝑚𝑒𝑐ℎ = 𝐷 ∗ 𝐷𝑃𝑎𝑑𝑗 𝑤𝑡 ∗ 𝐵𝐹 + 𝐵𝑙𝑜𝑐𝑘 𝑊𝑡

𝐵𝑂𝑊𝑚𝑒𝑐ℎ = 3000 ∗ 22.60 ∗ 0.786 + 100,000 𝐵𝑂𝑊𝑚𝑒𝑐ℎ@3000𝑓𝑡 = 153,291 𝑙𝑏𝑠

Mechanical Back Off Procedure:

a) Put RH torque in DS with full indicator weight

b) Adjust weight to BOW_mech

c) Put LF torque in DS for back off (unscrew thread connection)

Fishing

• A fish is any unwanted object downhole in a wellbore

• Can occur during drilling, completion, or production phases

• Examples: twisted off bit or drill pipe, wrenches, tools, etc.

• Fishing Tools

• https://www.youtube.com/watch?v=7-WqVgksKtk

• Weatherford Drilling Jars

• https://www.youtube.com/watch?v=z3WdcSrfvDM

https://www.youtube.com/watch?v=z3WdcSrfvDM

Fishing

• Parted Pipe

• Twist off

• Washout

• Cyclic stress

Fishing

• Cable & wireline

• Running logs

• Setting plugs (completions)

Fishing Economics

• Engineers must quickly perform economics to determine the path forward

• Call out a fishing service team and begin fishing operations

• Leave the fish where it is and sidetrack around it to finish drilling

• Leave the fish where it is and produce the well at current depth

• Plug and abandon the well

• Experience has great value in fishing

Fishing Economics

• Fishing Economics Decision Making

• This only considers the economics for the rig. What about for the company and delayed production? 32

𝐷 = 𝑉 + 𝐶𝑠 𝑅 + 𝐶𝑑

D = # of days allowed to fish for a breakeven NPV V = replacement value of fish ($) 𝐶𝑠= Estimated cost to sidetrack ($) R = daily cost of fishing tools and services ($/day) 𝐶𝑑= daily rig operating cost ($/day)