Petroleum Engineering 411 Well Drilling Lesson 28 SMD Well Control

Subsea Mudlift Drilling ( SMD ) Note Pump and ReturnLine

DESIGN PROJECT Your PETE 411 Design Project is Due in Dr. J-W’s Office by 5 p.m. on Monday, Dec. 9, 2002 Monday, Dec. 2 is set aside for you to get together with your team mates to work on the project during regular class hours.

Contents - Review of Conventional Well Control Kick Detection in SMD Kick containment in SMD Behavior of Real Gases in SMD Wells Well Control in SMD

Kick Detection & Well Control - Review - Conventional - Kick Indication (what is a KICK?) Kick Detection (confirmation) Kick Containment (stop flow into well) Circulate Kick out of hole Increase Mud Weight in hole (if necessary)

Circulate Kick out of hole Conventional Wait and Weight Method Old Mud Kick Kill Mud BHP = Constant Keep the BHP constant throughout

Gas Kick Behavior - Perfect Gas Maximum Choke Pressure = 1,000 psia. BHP = 6,000 psia 0.02 deg F/ft 0.00 deg F/ft 0.01 deg F/ft 23

Z-Factor - In Shallow Wells Gas Specific Gravity = 0.65 (S.G. of air = 1) 23

Shallow Gas Kick - Summary 0.02 deg F/ft Real Gas Ideal Gas PV = constant 23

Gas Kicks in Deep SMD Wells MudLine MudLift Pump As expected, most of the expansion occurs in the top 3,000 ft or so 23

Gas Kicks in Deep SMD Wells PV = ZnRT PV = constant 23

Gas Kick Behavior - Z-Factor Gas Specific Gravity = 0.65 (S.G. of air = 1) 3.0 30 60 pV=ZnRT 100 150 2.5 200 300 400 2.0 Compressibility (Z-Factor) Temperature, o F 1.5 1.0 0.5 5,000 10,000 15,000 20,000 25,000 Pressure, psig 23

~SEAWATER HYDROSTATIC PRESSURE Subsea Mudlift Drilling System FLOATER Surface Pump: Constant Rate Mudlift: Const. Inlet Press. ~SEAWATER HYDROSTATIC PRESSURE 10,000’ SEAFLOOR BOP MUDLIFT 30,000’ KICK What next?? 27

Kick Detection and Control 28

Kick Detection and Control Influx has stopped and pressures have stabilized ATM 28

Kick Detection and Control ATM 28

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SICP CONVENTIONAL 30

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Kick Detection Method Still Valid for SMD? Pit Gain Still valid Flow Rate Increase (Returns) Much Better Well Flows With Rig Pump Off … U-tubing ... Fluid Fill-up on Trips … More complicated Increased Hook Load Still Valid Drop in Standpipe Pressure Better Drop in BHP - MWD Still Valid Drilling Break Still valid Decreased Mud Weight (Gas Cut) Still valid 33

Well Control Summary Most Conventional kick detection methods are still valid New differential flow rate method - better - use with computer monitoring Lower standpipe pressure makes kick detection easier and faster Conventional well control can be adapted - with modifications 34

Well Control Summary cont’d Not necessary to shut well in … Seafloor pump controls the BHP Surface choke pressure generally does not affect wellbore pressures Well control training will be essential !! 35

General Summary Subsea Mudlift Drilling is a method that offers potential for lowering drilling costs in very deep waters. ( fewer casing strings, smaller rigs, less time on location, larger hole ) The method utilizes one or more small-diameter return lines from the seafloor to the surface. The drillpipe is not inside a return line. 36

Summary - cont’d A “mudlift” system is used in the return line thereby making a “dual-density” mud system possible. Wellhead pressure is maintained at seawater hydrostatic, so well is “dead” at all times Well control is quite similar to that in conventional drilling with a riser - There are some real advantages: higher margins, choke line DP, etc. 37

ATM THE END 38

~SEAWATER HYDROSTATIC PRESSURE U-Tubing in SMD ATM FLOATER ~SEAWATER HYDROSTATIC PRESSURE STATIC FLUID LEVEL BOP MUDLIFT 23

ANNULUS AND RETURN LINE SEA WATER HYDROSTATIC PRESSURE Static Pressures - SMD ANNULUS AND RETURN LINE DRILLSTRING PRESSURE SEAFLOOR DEPTH SEA WATER HYDROSTATIC PRESSURE PRESSURE 18