Operations & Wellsite Geologist PDF

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technical training 2005 Operations & Wellsite Geologist Stag Geological Services Ltd. Reading UK Revision C January 2004 technical training 2005 Operations & Wellsite Geologist Section 1 Operations & Wellsite Geolgy Chapter 1: Operations Geology Chapter 2: Wellsite Geologist Chapter 3: W...

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technical training 2005

Operations & Wellsite Geologist Stag Geological Services Ltd. Reading UK

Revision C January 2004

technical training 2005 Operations & Wellsite Geologist Section 1

Operations & Wellsite Geolgy Chapter 1: Operations Geology Chapter 2: Wellsite Geologist Chapter 3: Wireline Logs Chapter 4: Coring Chapter 5: Log Witnessing

Section 2

Reporting Procedures End-of-Well Report Daily Reports

Section 3

Wellsite Geological Processes Chapter 1: Formation Evaluation Chapter 2: Lag Time Chapter 3: Mudlogging Unit Chapter 4: Gas Detection Chapter 5: Sedimentary Petrology Chapter 6: Cuttings Evaluation

Section 6

Measurement While Drilling

Section 7

Horizontal Well Formation Evaluation

Section 8

Geosteering

Section 9

Log Examples

Section 10

Geosteering Case Study

Section 11

Log Interpretation Charts

Figure 1: Table of Contents

Operations Geology Introduction Operations and Wellsite Geology support plays a crucial role in the success of drilling and production ventures. Typically the Operations Geologist will be a member of the exploration department of the operating company although now, in many cases, he is responsible to the project or drilling manager and thus may have a dual reporting role. The drilling department will require information during the planning stage regarding the detailed geological stratigraphy, targets, offsets, problem formations and the exploration department will require the collection and quality control of geological data as the well is drilled. The Operations Geologist will have been assigned at the beginning of the well planning phase and is the main communication link between the exploration and drilling departments. He is a vital interface between the rig and the office and is also responsible for the provision of wellsite contractor services. Partners will require the Operations Geologist to provide them with data and operational information in a timely manner. The Wellsite Geologist is responsible the wellsite geological data collection and quality control of contractor’s services under the supervision of the Operations Geologist. He may not have been involved in the planning process but obviously needs to be sufficiently briefed prior to the commencement of the job in order to be fully aware of the duties and responsibilities required of him. The Operations Geologist and the Wellsite Geologist may be full time employees of the Operator or specialist consultants. Consultants are usually very experienced in both drilling and formation evaluation; many having begun their careers as Mudloggers and so gained an appreciation of many the different disciplines involved in drilling, evaluating and completing wells. It is often the case that full time employees of oil companies are given operations and wellsite roles early in their careers as a stepping stone in their overall development. The latter will need a great deal of supervision, guidance and training from their managers as well as constructive support form the contractor’s personnel that they are dealing with.

General Duties of the Operations Geologist • Be an active member of the project team providing geotechnical support to design and execute a well plan to meet exploration objectives • Provide a Data Acquisition program to meet licence members objectives and government requirements

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Operations Geology • Compile the G&G section of the drilling program. • Identify and select wellsite and post well analysis services • Manage and QA formation evaluation Contractors and services • Provide office based technical support to the rig team • Receipt of data from all formation evaluation service providers • Logistical support for wellsite Formation evaluation services • Focal point for distribution of daily updates and communication for partners and government bodies • Review of actual versus planned performance indicators • Cost control of formation evaluation services • Compilation of Completion Log • Production of End-of-Well report

Well Planning Establishing a time frame for all activities is critical to the success of the project management. All critical path activities should be carried out efficiently and smoothly; other activities need to be conducted in a manner that will not adversely affect critical path activities and particularly to the effect that they will not become critical path activities themselves. The lack of key geological information can have a serious impact on the critical path. For example the lack of site survey information may delay rig choice and well path planning and the lack of a pore pressure profile will impact casing and wellhead design.

Tasks for the Operations Geologist • Co-ordinate the needs of the exploration team and compile a DAP • Organise vendor presentations for the project team • Undertake vendor appraisals and organise contracts • Meet deadlines for the Detailed Drilling Plan: Pore Pressure/Fracture Pressure Profiles, Site Survey data, Geological hazards • Prepare a Data Acquisition Procedures manual • Attend partner and government agency meetings • Organise and facilitate pre-spud meetings and training

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Operations & Wellsite Geology

Operations Geology Well Planning Process

Well Planning Process Asset Team Requirements

Wellobjectives objectives Well

Increase production & reserves Increase production & reserves Increase efficiency & decrease project development cost Increase efficiency & decrease project development cost Flexible design: producer & injector Flexible design: producer & injector Improve Enhanced Oil Recovery/water-flood Improve Enhanced Oil Recovery/water-flood Exploration tool in reservoir evaluation Exploration tool in reservoir evaluation Any combination of the above Any combination of the above

Geology Geophysics

Fluid Fluid Properties oil, water, gas ! API Gravity, Viscosity ! PVT Data !

Archives !Field

!Petrophysicss !Engineering !Simulation !Special

DataAcquisition Acquisition Data Analysis &&Analysis

Petrophysics (Logs)

!

Gross column ! Net column

WellProposal Proposal Well

!

© 1999 Stag Engineering Services Limited

! !

Petrology Mineralogy Clay Content

Productivity/injectivity

Φ

Well location Drilling & completion details ! Well treatment ! Well type producer, injector, Obs. ! Status Shut In, Abd, Prod, etc ! Artificial Lift System ! Rates, oil, water, gas, choke size ! Cumulative oil, water, gas

!

!

!

!

Lithology Fluid Saturation !Geological Markers

(inc. Reservoir Deliverables) (inc. Reservoir Deliverables)

Studies

Petrophysics (Cores) ! Φ & Horiz. & vert. k.

!

Surface location & ID, well length, orientation & targets Surface location & ID, well length, orientation & targets Correlation wells, regional data, sections & maps Correlation wells, regional data, sections & maps Prognosed Geology, formation tops, FBG, temperature Prognosed Geology, formation tops, FBG, temperature Formation evaluation, logging, coring WSG Formation evaluation, logging, coring WSG Expected reservoir pressures & fluids Expected reservoir pressures & fluids Recoverable reserves, production forecast oil, water & gas Recoverable reserves, production forecast oil, water & gas Completion requirements inc. sand control &/or stimulation Completion requirements inc. sand control &/or stimulation Completion design & predicted flowing conditions Completion design & predicted flowing conditions Potential for for future well interventions Potential for for future well interventions Quality indicators Quality indicators

Studies

!Geology

Seismic Sections ! Maps ! Structures !

Reserves Field Block ! Area of Interest ! Reservoir ! Well ! !

ReservoirAnalysis Analysis Reservoir

- Original oil/gas in place & recovery to date - Original oil/gas in place & recovery to date - Drive mechanisms - Drive mechanisms - Changes of OWC & GOC with time - Changes of OWC & GOC with time - Rock & fluid characteristics of all zones - Rock & fluid characteristics of all zones - Production/completion problems e.g. sand, wax - Production/completion problems e.g. sand, wax - Depletion of reservoir pressure with time - Depletion of reservoir pressure with time - Production forecasts assuming no EOR - Production forecasts assuming no EOR - Field/reservoir recovery factors - Field/reservoir recovery factors - Remaining recoverable oil & gas reserves - Remaining recoverable oil & gas reserves - Identify/explain zones of low recovery &/or bypassed oil - Identify/explain zones of low recovery &/or bypassed oil - Construct reservoir model to predict reservoir performance - Construct reservoir model to predict reservoir performance

Methods Methods

Material balance calculations Material balance calculations Volumetric analysis Volumetric analysis Decline curve analysis Decline curve analysis Log evaluation Log evaluation Pressure transient analysis Pressure transient analysis Analytic models e.g. JTI Horizontal Analytic models e.g. JTI Horizontal EOR screening EOR screening Geostatistics & reservoir characterization Geostatistics & reservoir characterization Reservoir simulation Reservoir simulation

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Figure 1: Well Planning Process The project team will have determined a set of well objectives which will form the basis of the Detailed Drilling Plan (DDP). This will be compiled from G&G data supplied by the Operations and Exploration department. In turn the DDP will allow the Authorisation for Expenditure (AFE) proposal to be written and submitted for approval. The AFE then becomes the most important document in the planning and execution phases since it provides the controls and limitations for the entire project.

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Operations Geology

Figure 2: Detailed Drilling Plan

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Operations Geology

Figure 3: AFE Template

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Operations Geology Generalised G&G data needs to be submitted to the Drilling Engineers at an early stage in order that the initial well plan and design can begin. This may be up to one year before spud date. The G&G data will necessarily be lacking detail but the generalities of a planned logging programme will influence the drilling plan. Some logging tools will, for example, be mud specific and will need to be identified early on. The Geological Program and the DDP will evolve over time. They will be compiled by individuals with input from many other contributors. Regular meetings need to be held with project and exploration team members to communicate goals and plans and solicit constructive feedback. All planning documents need to be verified by team members before being submitted for approval. The distribution of all documents will be controlled in order that amendments may be managed correctly and that all individuals are using the most up-to-date versions of them.

Summary of Operations Geological Issues for Well Planning Well Objectives • Should take into account all of the above points and will include production criteria, reservoir exposure, coring, testing and safety issues. • Risks- Mitigations • MWD/LWD • “Wireline” logs • Other formation evaluation services • Communications & Team Work

Critical G&G data for Detailed Drilling Plan The following data is critical for the early development of the detailed drilling plan. They impact rig selection, casing and wellhead equipment selection. • Site Survey/Shallow hazards • Pore Pressure Prognosis • Fracture Pressure Prognosis • Geological Hazards

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Operations Geology Site Survey/Shallow hazards The site survey should be carried out at least six months prior to spud and will normally consist of the following components: • Positioning • Sea-Bed Investigations • Sub-Bottom Investigations

GPS Differential Corrections

Seismic Relection (sub-surface)

Sidescan Sonar (surface area)

Figure 4: Components of a Site Survey

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Operations Geology Positioning Geodesy: Measuring the Earth 3 Reference Surfaces: • Topography • Geoid • Ellipsoid (Spheroid) 2 Measurement Systems: • Geographical • Projections Ellipsoid is the basic reference surface Heights are often related to Geoid (MSL) GPS heights are related to Ellipsoid Latitude/ Longitude referenced to Ellipsoid Lat/ Long ALWAYS need associated DATUM Projections (UTM etc.) ALSO need DATUM

Locating & Orientating the Ellipsoid in space requires 8 constants to be defined: • Size & shape of Ellipsoid (2 parameters) • Direction of minor axis (2 parameters) • Position of the centre (3 parameters) • A zero coordinate (1 parameter) • Naming of Datums can be problematical Venezuela has 17 Datums in Maracaibo 3 are called "Maracaibo Cathedral”

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Operations Geology Ellipsoids always associated with Datums • Ellipsoid names can be duplicated • Ellipsoid PARAMETERS are best • There are several “versions” of ED50 Datum • All convert to/from WGS 84 DIFFERENTLY • 54 deg N/ 3 deg E (ED50 / ED87 Equivalent): --53d 59m 57.51s N/ 2d 59m 55.08s E (WGS 84) • 54 deg N/ 3 deg E (ED50, old “general”): --53d 59m 57.29s N/ 2d 59m 54.87s E (WGS 84) • Approx. 8 metres variation • Vessel navigation, typically (95%) 3 - 5 m • Bathymetry: depends on depth • Sidescan sonar, typically (95%, relative) 5 - 8 m • Sparker, boomer, airgun (95%, relative)3 - 5 m • Hydrophone arrays (95%, relative) 5 - 8 m • RMS Sidescan6 - 9.5 m • RMS sources4 - 7 m • RMS hydrophones

Sea-bed Investigations Sea floor cores and samples are taken to determine the nature and strength of sediments and to calibrate side-scan sonar and bathymetry data. This is particularly important for Jack-Up rigs in order to prevent leg instability.

Sea-floor samples Grab sampler This is dropped under its own weight and is spring triggered on impact. The bucket rotates, trapping the sample. It is limited to the top 30-40 cm of seabed. The sample is collected with minimal disturbance.

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Grab & Core Sampling Required to “ground truth” sidescan and bathymetry data by calibrating records to sample types. Samples taken at points in the survey area identified by sidescan. Enables confident extrapolation of very shallow sediments over a wide area Free-Fall Release Gear Weight

Rotating Bucket

Fin

Weight Core Tube Piston Coil Spring

Core Liner

Grab sampler dropped under own weight. Spring triggered on impact. Bucket rotates, trapping sample. Limited to top 30-40 cm of seabed. Sample collected with minimal disturbance.

Weight

Tough Nose & Core Catcher

Figure 5: Grab & Core sampling

Core sampler Gravity Corers - these corers are available in a wide range of options, with lengths of corer tubes from 1m to 10m in a variety of diameters, with or without internal tube liners. With tube barrels of either mild steel (with a choice of finishes) or stainless steel. The tube barrels are supplied with or without cutters. The largest Gravity Corer supplied to-date, had a barrel length of 32m and weight 10 tonnes.

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Operations Geology

Figure 6: Grab & Core sampling

Side-scan Sonar The intensity of sound received by the sidescan-sonar tow vehicle from the sea floor (backscatter) provides information as to the general distribution & characteristics of the superficial sediment. This may include channels, boulders, subsidence (pock marks), sea-bed features and sub-sea structures e.g. wellheads, pipe lines and shipwrecks. In the lower left schematic, strong reflections (high backscatter) from boulders, gravel & vertical features facing the sonar transducers are white; weak reflections (low backscatter) from finer sediments or shadows behind positive topographic features are black. The sea floor is typically surveyed in swaths 100-500 meters wide; the swaths are mosaiced together to form a composite image of the survey area.

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Operations Geology

Figure 7: Sidescan sonar

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Operations Geology

Sidescan Example: Port Hunter

Figure 8: Sidescan Sonar example

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Operations Geology

Figure 9: Pockmarks

Seismic Reflection Profiling Seismic reflection profiling is accomplished by towing a sound source that emits acoustic energy at intervals behind a survey vessel. The transmitted acoustic energy is reflected from boundaries between various mediums of different acoustic impedances (i.e. the water-sediment interface or between geologic units). Acoustic impedance is defined by the bulk density of the medium & the velocity of the sound within that medium. The reflected acoustic signal is received by a shiptowed hydrophone (or array of hydrophones), which converts the reflected signal to a digital or analog signal. The signal from the hydrophone can be logged, filtered & displayed. The digital data can then be gathered with information from adjacent hydrophones to enhance the signal to noise ratio. A shallow seismic survey is commonly run over 6.5 square km area with the spud location at its centre. It will identify shallow geological features such as channels, shallow sands and shallow gas deposits down to the depth at which casing would normally be set at the BOP installed.

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Operations Geology

Figure 10: Seismic Reflection Profiling The Sparker The Sparker is a relatively high powered sound source, dependent on an electrical arc which momentarily vaporises water between positive & negative leads. The collapsing bubbles produce a broad band (50 Hz - 4 kHz) omni directional pulse which can penetrate several hundred meters into the subsurface. Resolution is 2-5 metres. Hydrophone arrays towed nearby receive the return signals.

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Operations Geology

Figure 11: Sparker

The Pinger (CHIRP) The Geo Acoustics GeoChirp is a sub-bottom profiling system for high resolution shallow geophysical surveys. The Chirp concept uses advanced frequency modulation (FM) & digital signal processing to attain good penetration of the subbottom layers whilst achieving higher resolution records. The Geochirp is configured with the electronics bottle mounted on the towfish & the receiving hydrophone attached & towed directly from the rear of the fish. Data from the GeoChirp may be displayed on a variety of graph...