Elevations, Heights and Datums in Data

Models and the “Real World”

PPDM Perth Data Management Conference

9 September 2010 – Perth

Jim Stolle – TGS

Paul Haines – Noah Consulting

2

A Typical Drilling Rig

1 Crown Block and Water Table

2 Catline Boom and Hoist Line

3 Drilling Line

4 Monkeyboard

5 Traveling Block

6 Top Drive

7 Mast

8 Drill Pipe

9 Doghouse

10 Blowout Preventer

11 Water Tank

12 Electric Cable Tray

13 Engine Generator Sets

14 Fuel Tanks

15 Electric Control House

16 Mud Pump

17 Bulk Mud Components Storage

18 Mud Pits

19 Reserve Pits

20 Mud Gas Separator

21 Shale Shaker

22 Choke Manifold

23 Pipe Ramp

24 Pipe Racks

25 Accumulator

From: The Univ. of Texas at Austin

KB

DF

RT

From: http://www.osha.gov/SLTC/etools/oilandgas/illustrated_glossary.html

3

Real World vs. Logical

Real World

Kelly Bushing

Rotary Table

Derrick Floor

Casing Flange

Ground Level

Sea Level

Mud Line

Logical

Datum

Reference

Elevation

Height

Depth

4

Elevation and Height – The Basics

GroundElevation

Mean Sea Level

Heights – Measured above Ground Level

Elevations – Measured above Mean Sea Level

Depths – Measured below a reference point

Height above GL

Elevation

above MSL

Depth below a reference point

5

Real World Attributes around the Rig

Real World

Kelly Bushing

Rotary Table

Derrick Floor

Casing Flange

Ground Level

Sea Level

Mud Line

Attributes

Kelly Bushing Height*

Kelly Bushing Elevation

Rotary Table Height*

Roatry Table Elevation

Derrick Floor Height*

Derrick Floor Elevation

Casing Flange Height*

Casing Flange Elevation

*Not in PPDM data model

6

Logical Attributes around the Rig

Logical

Datum

Elevation

Reference

Height

Depth

AttributesPermanent Datum*

Elevation Reference Datum

Elev. Ref Datum Elevation*

Depth Datum (Working)

Depth Datum Elevation

Height Datum*

Height Datum Elevation*

Ground Level Elevation

Mean Sea Level Elevation*

Water Depth Datum

Water Depth

*Not in PPDM data model

7

Data Model Treatment

8

Schlumberger GeoFrame

Heights – Does not capture

Elevations – Measured above PD

Depths – Measured below Working Datum

(from Well / Borehole tables)

Working-Datum/CODE

Working-Datum/ELEVATION

Permanent-Datum/ELEVATION

GROUND_ELEV

Ground Level

Kelly Bushing

Mean Sea Level

Mud LinePermanent-Datum/CODE

9

Schlumberger Seabed

Heights – Does not capture

Elevations – Measured above a Vertical Reference

Depths – Measured below a different Vertical Ref

(from Coordinate-System & Position tables, linked to Well & Borehole tables)

Working-Coor-Syst/Vertical-Ref

Position/Elevation

Position/Elevation

Ground Level

Kelly Bushing

Mean Sea Level

Mud Line

Position/Elevation

Permanent-Coor-Syst/Vertical-Ref

10

Paradigm EPOS

Heights – Does not capture

Elevations – Depends – see note below

Depths – Measured below Measurement Ref

(from Well-database / Well-information tables)

Ground Level

Kelly Bushing

Mean Sea Level

Mud Line

MEASUREMENT_REF

DATUM_ELEVATION

ELEV_MEAS_REF

DEPTH_DATUM_ELEVATION ?

EPD

DATUM_ELEVATION

MSL is implicit permanent datum

Note: If DATUM_ELEVATION = GL in Paradigm, then DEPTH_DATUM_ELEV = EPD + ELEV_MEAS_REF

If DATUM_ELEVATION = MSL in Paradigm, then DEPTH_DATUM_ELEV = ELEV_MEAS_REF

11

Landmark R5000

Heights – Does not capture

Elevations – Measured above implicit MSL

Depths – Measured below Depth Datum Type

(from Well-Master table & Elev-Info table)

DEPTH_DATUM_TYPE

DEPTH_DATUM

GROUND_ELEV

MSL is implicit

Ground Level

Kelly Bushing

Mean Sea Level

Mud Line

12

Open Spirit 2.9

Heights – Does not capture

Elevations – Measured above Vertical Datum

Depths – Measured below Elevation Datum

(from Well table & Wellbore table)

Ground Level

Kelly Bushing

Mean Sea Level

Mud Line

ELEVATION_DATUM

ELEVATION

GROUND_ELEV

MSL is implicit vertical datum

13

PPDM 3.8

Heights – Does not capture

Elevations – Measured above Elevation Ref Datum

Depths – Measured below Depth Datum

(from Well table)

Ground Level

Kelly Bushing

Mean Sea Level

Mud Line

DEPTH_DATUM

DEPTH_DATUM_ELEV

GROUND_ELEV

ELEV_REF_DATUM

14

Comparing Data Models to the Oilfield

15

Attribute Ambiguities

The Level of the Sea?

MSL

LAT

SL

MWL

The Ultimate Origin?

Permanent Datum

Elevation Reference

Datum

16

Temporal Ambiguities

Changes over time

What happens when rigs change out on a particular well

The Depth Datum can change

The Datum Elevation for the same reference can change

Are measurements taken at different times corrected?

Is this handled properly or at all in data models?

PPDM – Well Version table

R5000 – Well Master Alt table

Seabed – Alternate Elevation

17

PPDM

PositivesIt works

Consistent naming

Relatively comprehensive in datums and elevations

Straightforward to model

Opportunities for ImprovementNo Heights

No Permanent Datum

No value for Elev-Ref-Datum

Ground-Level-Type

Mixes Water-Depth and Well-Depth references

Changes in datum names or values over time

Some definitions re-tooled

18

Summary

Real oilfield things and logical concepts

Various data models address topic differently

Potential confusion and ambiguity lessened if:

Use of “height” in addition to datum and elevation

Use of permanent datum and elevation datum

Tighten up definitions and reference tables

Changes over time compromise data quality

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Noah Consulting LLC.

TGS