horizontal well geosteering planning, monitoring and geosteering

8/12/2019 Horizontal Well Geosteering Planning, Monitoring and Geosteering

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28 Journal of Canadian Petroleum Technology

Horizontal Well Geosteering: Planning,Monitoring and Geosteering

R. MOTTAHEDEHUnited Oil & Gas Consulting Ltd.

THIS PAPER IS BEING PUBLISHED AS A CASE STUDY AND HAS NOT BEEN PEER REVIEWED.

Introduction

Reducing Costs and IncreasingPerformance for Optimal Well Results

Whether drilling a long reach horizontal well in heavy oil or a

tight gas play, the basic requirements for a successful well are:

1) Planning the optimal path based on the current knowledge of

integrated geological/geophysical models.

2) Monitoring the progress of the well through real-time up-

dates by well profiles and 3D visualizations.

3) Continuously re-mapping to identify the true stratigraphic

position (TSP) of the bit relative to the reservoir. This

Abstract

The geosteering process should not be seen as a process solely

designated for the most expensive or highest profile horizontal

wells. It can be regarded as another tool for improving the odds

of success by remaining in the productive zone for longer periodsof drilling. Also, it can be used to optimize the positioning of a

horizontal wellbore in the sweet spots within the reservoir.

The current process has been successfully applied to large in-

fill drilling programs at over 40 wells for heavy oil, tight gas, con-

ventional oil and gas plays and for Mannville coalbed methane

(CBM) in Alberta. The service has been provided irrespective

of location, as long as the Wellsite Information Transfer Stan-

dard Markup Language (WITSML)/Pason Satellite service is

available.

Exploration and production (E&P) companies are continu-

ously being driven to reduce the cost per barrel of oil equiva-

lent (BOE). E&P needs and technologies related to advanced

and accurate directional drilling, communication of vital data in

real-time through the internet, as well as reduced cycle time as-sociated with advanced forward-looking 3D geo-modelling and

visualization technologies (Figure 1), are currently converging.

The motivation to reduce costs has been responsible for ad-

vancing the horizontal well geosteering process by incorporating

the Measurement While Drilling (MWD) tool into mainstream

drilling practices. The universal economic benefits gained can be

found in all resource play types (conventional oil and gas, heavy

oil, tight gas and coalbed methane).

It is important to note that the process described here is essen-

tially collaborative. For best results, there must be cooperation

between the E&P operational geologist, wellsite geologist, direc-

tional driller and geo-modelling staff, as well as the engineering

consultants involved in the project (i.e. the team as a whole).

information is used to provide advice to the drilling team for

staying in the zone of interest while drilling.

4) Timely reporting on the updated road map for the horizontal

well to provide the information necessary for drilling ahead

of the bit.

Depending on the depth and/or rock type, the speed of drilling

can range from very fast (200 m/hr in shallow heavy oil horizon-

tals) to very slow (3 to 10 m/hr in tight formations). For fast orslower drilling, the geosteering process is used as a planning and

monitoring tool. This reduces guesswork in the drilling process

which translates into less drilling time for a given well, ultimately

decreasing the total cost and increasing profits. The 3D geo-models

can be updated every few minutes for structural changes and pe-

riodically for characterization of gamma ray (GR), resistivity and

other reservoir attributes.

Another benefit for operators working in reservoirs that have

multiple rigs drilling is that the information gathered and processed

will influence and change the 3D mapping window (or highway)

for current or subsequent wells. Just in time modelling reduces

re-drill costs associated with sidetracks.

Geosteering a horizontal well while drilling is not only impor-

tant, it is also profitable. The controlled placement of wells formitigation of water or gas is another reason why geosteering can

be important for operation geologists, reservoir engineers, and for

E&P companies. Although the complexity of the geological struc-

tures and changes in the reservoir quality can be overwhelming,

automated gathering of MWD data, monitoring, frequent 3D map-

ping/characterization/visualization and reporting is now achiev-

able and easier to use with current advanced systems.

There are also other operational cost savings associated with

this just in time mapping process. Faster and more productive

drilling through the sweet spots in a reservoir can mean operational

time saving. This is particularly true in tight gas wells and in hard

formations. Longer productive reservoir intervals are exposed in

the wellbore, resulting in higher productivity. Also, drill bits last

longer, resulting in more cost savings.

CASE STUDYCASE STUDY

FIGURE 1: Convergence of technologies for geosteering.


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November 2008, Volume 47, No. 11 29

Advanced Directional Drilling Technologies

Advances in directional drilling aimed at geological targets arewell recognized today. These include increased accuracy in the

placement of extended horizontal wellbores based upon initialspecs. Just in time 3D mapping is a promising area that can addvalue to E&Ps by reducing the inherent geological risk and uncer-tainty with any drilling program.

Communication Technologies

A key component of the current synergy is advanced communi-cation technology. Data must be available as soon as it is needed.Current needs require immediate data access to vital well informa-tion in order for effective decision-making to influence the pathof horizontal wellbores. There are currently systems that deliver

the data from the wellsite using the Wellsite Information TransferSpecification (WITS) format through electronic data retrieval sys-tems or Electronic Drilling Recorders (EDR). Data from EDR sys-tems are accessible through secure websites in Log ASCII Standard(LAS) report format.

The WITS format has been upgraded to WITSML that wasfirst used in Europe. This format has now been available in NorthAmerica for over three years. Operators such as Statoil, BP andShell, who have been joined by several major service companies,have initiated the future of data acquisition. The WITSML processis consumer-driven (E&P) and its interfaces are comprised of twotypes: publish/subscribe and store.

The significance of this type of access is that the subscribeformat is comparable to an electronic news service where informa-

tion is continuously updated, allowing the consumer to choose thefrequency and type of information they would like updated, and isvendor neutral.

Using horizontal well drilling as an example, several types ofdata streams that may need frequent updating for geosteering, suchas gamma ray (GR) logs, well trajectory data and/or rate of pen-etration (ROP) can be delivered to the dynamic geo-model on awhile drilling basis. This allows for real-time monitoring andsubsequent re-mappings.

Reduced Cycle Time Using Advanced

and Automated 3D Geo-modelling

Technology

The E&P, consulting and service companies initially produceintegrated geo-models using geological and geophysical data. Thepre-drill models integrate all available data from the rig and col-laboration between the team.

These geo-models can contain as few as three wells to over1,000 wells. The example in Figure 2 illustrates a horizontal in-

jector in a small oil reservoir. The pre-drill model had eight wellsand a 3D seismic generated surface. This model also integratedstrip log porosity data for enhancing the model.

At the outset, the geo-model is used to plan the path of the heavyoil or tight gas horizontal wells through previously mapped outcharacterizations.

Example 1 (see Figure 3) shows a proposed and an actual well

trajectory providing hydrocarbon pore volume (HCPV) data of aheavy oil well in southern Alberta.The automated 3D mapping, characterization and visualiza-

tion, which are monitored and tested frequently, are accomplishedusing commercially-available 3D geo-modelling software andtechnology where the pre-drill model is updated at required fre-quencies. The examples provided here are from United Oil & GasConsulting Ltd.s SMART4D modelling software. United providesthe SMART Drilling report to a number of companies at any onetime.

Several features of these models include:

1) The enabling of accurate well planning for horizontal wellsthrough the 3D reservoir target window.

2) Monitoring capability with real-time data using standardssuch as WITSML.

3) The geological context for determining the true stratigraphicposition of the bit.

4) Forward-looking window providing the driller with a view tothe target.

Periodically, strip-log data from the wellsite geologist is inte-grated into the geo-modelling/geosteering profile while drilling.The geo-model results are provided as a report back to the clients.These reports consist, not only of 3D views of the planned and ac-tual drilling, but also along the length and plan distance from thewell centre. After drilling, newly acquired logs are incorporated

back into the model. All of the real-time and final reports are pro-vided through a secure website.

Case Studies

The following heavy oil example in northeast Alberta shows thedegree of mapping details for the path of a horizontal well. The res-ervoir contains hundreds of extended horizontals. Most wells havetops implemented at every 50 m of length.

Example 2 (see Figure 4) shows that once geologists implementthe tops by positioning an independent marker above and belowthe trajectory (using the gamma ray log response, offset well infoand trajectory position), the automated geo-model implements thetop within a few minutes (continuous surfaces mapped in the ex-ample as top and base). Once this mapping process is completed, itcreates the window for drilling the next infills prognosis.

To illustrate the point, Example 3 (see Figure 5) in the same

reservoir shows existing wells with no tops implemented at thisstage of mapping. These are already drilled and logged locationsfor which data has not been incorporated into the model, and yet

FIGURE 2: While drilling visualization and characterization.Visualizing trajectory and trace data from MWD.

FIGURE 3: Example 1: Heavy oil geo-modelling. Horizontal well

trajectory with HCPV zone data.


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the previous prognosis is consistent with the actual results. There-fore, Example 2 indicates a proactive process that maps out the

road map for the next set of infills. The increase of the gamma ray

log response corresponds well with the mapped surfaces and the

trajectory path, even without a single implemented top.

This textbook example is a result of conducting a detailed pre-

drill model, which can pay dividends for infill drilling programs.

The economic benefits are obvious when the outcome can assist in

longer time spent in the pay zone and avert costs associated with

sidetracks, etc.

The next examples are cases of tight gas in the Jean Marie

(Figure 6) Formation in northeastern British Columbia and the

Shunda (Figure 7) Formation in Central Alberta. The geosteering

process is the same; a pre-drill model is used in the starting posi-tion of drilling, while trajectory and other log data such as GR and

ROP, gas shows, etc., are updated while drilling.

The well planning and monitoring capabilities are used andthe geosteering process proves beneficial for providing additionalguidance for the remaining well length, thereby optimizing the

path when it is most advantageous to do so.The well placementis monitored continuously through top views (Figure 8) and sideviews along the length (Figure 9). Also a plan distance from thewell centre is available.

Figure 10 shows an example of a Mannville CBM well in Al-berta. The coal was quite thin (~2m), and other than some opera-tional issues, the well penetrated the zone for about 90% of thetime. Figure 11 is part of a 40-well drilling program. ROP and GRwere used for geosteering. ROPs of up to 300 m/hr were commonin this drilling program, with multiple wells drilling concurrentlyin one project area.

Collision Avoidance

Collision avoidance in tightly spaced and extended horizontalwells is a real issue. Its importance extends to any reservoir,

whether oil or gas. Safety and operational cost considerations aremajor concerns to operators and field personnel. The risk of losingan existing oil producer or getting stuck in the hole leads to costly

FIGURE 4: Example 2: Heavy oil geo-modelling. Refreshed HW

profile with control points.

FIGURE 5: Example 3: Heavy oil geo-modelling. Refreshed HWprofile with NO control points.

FIGURE 6: While drilling reservoir & trajectory visualization.Incorporating real-time data.

FIGURE 7: Time-based model of structure and porosity.

FIGURE 8: L Time-based model of proposed vs actual trajectories.

FIGURE 9: Time-based model of structure and porosity along the

horizontal trajectory.


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November 2008, Volume 47, No. 11 31

down time, as well as lost revenue from poor well placement on thenew drill. Other concerns include the additional cost of sidetracks,drill bit damage and equipment loss. While drilling, geo-model vi-sualization provides the visual check for errors associated with sur-veys of horizontal wells.

The example shown in Figure 12 is from the Dina Sands Res-ervoir in the Hayter Field in southeastern Alberta. Development inthe field has progressed to the point that there are several dozenhorizontal wells within each section (one square mile).

A typical long-reach horizontal well (~1,500 m) with an averagesurvey error uncertainty of one degree from the kick-off point canhave up to 25 m of potential drift (Figure 13).

Figure 14 shows a perspective view of porosity distribution andtrajectories in this reservoir.

Conclusions

Available technologies and services have converged to pro-vide on-demand mapping technologies and services to enhance

FIGURE 11: Bluesky Oil Reservoir in Seal Field, Alberta.Horizontal drilling program showing 3D view while drilling (redline) and proposed path (light green). Dark green wells have already

been drilled.

FIGURE 12: Visualizing the trajectories on horizontal wells.

FIGURE 10: Mannville CBM horizontal drilling through thin coalbed ~2m thick. The profile shows GR, gas shows, ROPs and differential

pressure. The left chart shows the offset log.


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well placement and productivity in horizontal wells. E&P com-

panies who use advanced directional drilling, communication and

3D geo-modelling technologies can take advantage of this to re-

duce the risks while providing better tools for their drilling opera-

tion teams.

Real-time planning and monitoring capabilities for faster

drilling of horizontal wells (heavy oil) and geosteering capability

for slower drilling (hard formations or coals) are accessible for all

horizontal wells. The geosteering technologies and services have

advanced to the point that they should be incorporated into the op-

erational process of any horizontal or directional drilling program

in order to increase operational efficiencies and profitability. With

the volume and emphasis on horizontal well drilling programs in

the past number of years, the costs for geosteering technologies

have also been reduced to make them more widely accessible.

Mitigation of gas and water in oil reservoirs and collision avoid-

ance are two more reasons for incorporating geosteering into the

drilling process.

The collaborative process between E&P operational geologists,

geosteering consulting services, directional drillers and real-time

data providers is required in every stage of drilling operations for

successful geosteering.

Using the forward-looking window for drilling approach, the

team in the field and in the office will benefit from improved com-

munications, which, in turn, increases profitability, thereby accom-

plishing the requirement for cost savings.

Acknowledgements

All images reported are from various United Oil & Gas Con-sulting Ltd.s projects using SMART4D Modelling, integratedgeo-modelling software and geosteering application.

ProvenanceOriginal Petroleum Society manuscript, Horizontal WellGeosteering: Planning, Monitoring, and Geosteering (2005-017CS),first presented at the 6th Canadian International Petroleum Conference (the56th Annual Technical Meeting of the Petroleum Society), June 7-9, 2005,in Calgary, Alberta. Abstract submitted for review November 18, 2004; edi-torial comments sent to the author(s) October 26, 2005; revised manuscriptreceived July 25, 2007; paper approved for pre-press July 30, 2007; finalapproval October 27, 2008.

FIGURE 13: HW Trajectory detailed view. Cones of uncertainty around the survey from kick-off point (KOP)top view.

FIGURE 14: Visualization of survey errors for mitigating wellbore collision.

Authors Biographies

Rocky Mottahedeh,P.Eng., P.Geol. is thePresident of United Oil & Gas ConsultingLtd. Rocky graduated from the Universityof Toronto in 1981 with a B.Sc. in geo-logical engineering. He has 26 years of oiland gas experience with an emphasis onnew technology and integrated reservoirstudies in gas, coalbed methane, oil sandsand heavy oil at E&P companies in Canadaand internationally. In the past ten years,Rocky has been involved in technology de-

velopment (SMART4D Modelling) focused on geo-modelling andgeosteering through his company, United Oil and Gas ConsultingLtd.

horizontal well geosteering planning, monitoring and geosteering

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