HORIZONTAL DRILLING: AN ENABLING TECHNOLOGY

D.A. GUST

this article begins on the next page FFTHE PETROLEUM SOCIETY OF CIM ABSTRACT Horizontal drilling is a core technologyfor reservoir development. This paper is an overview of today's horizontal drilling technology and a discussion of how the technology may be used in thefuture. Thefollowing technologies will be discussed.- Geosteering- Most horizontal wells drilled today are placed in the reservoir based upon reservoir or geological parameters. MWD logging tools are being used to guide the well path as the well is being drilled This paper will discuss the various logging sensors availahle and how they can be used forgeosteering. Underbalanced Drilling Systems These systems are being developed to minimize formation damage and ensure that the maximum production potential of each horizontal well is realized Underbalanced drilling isbeingusedprimarilyinpressuredepletedreservoirs. This paper will review the different techniques being used and discuss the relative merits of each. D.A. Gust Sperry Sun Drilling Services of C,anada Muftle Lateral Wells, These wells are being used to drain single reservoirs more efficiently and to drain multiple reservoirs. Use of multiple lateralscan also reduce the number of surface locations, which lessens environmental impact and reduces overall project cost. The multiple laterals can be drilled using either open hole sidetracks, or newly developed casing systems that will permit controlled reentry into each of the laterals. This paper pre,sents an overview of the types of wells being drilled today anct discusses potential uses of the technology in the future. Short Radius Drilling Sotemn- Short Radius Drilling Systems have been in usefor many years. These systems have, however, had some significant limitations. Newsystems have been developed which include MWD tools for steering control The development of composite fibre drillstring components will permit the use of steerable systems for drilling the horizontal interval This paper discusses the potential uses of short radius systems and hol,v they will interface with other emerging technologies. This paper is to be presented at the 46th Annual Technical Meeting of The Petroleum Society of CIM in Banff, Alberta, Canada, May 14 - 17, 1995. Discussion of this paper is invited and may be presented at the meeting if filed in writing with thetechnical program chairman prior to the conclusion of the meeting. This paper and any discussion filed will be considered for publication in CIM journals. Publication rights are reserved. This is a pre-print and is subject to correction. Horizontal Drilling: An Enabling Technology PAPER 95-03

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THE PETROLEUM SOCIETY OF CIM

Horizontal Drilling:An Enabling Technology

DA GustSperry Sun Drilling Services of Canada

PAPER 95·03

.-...This paper is 10 be presenled at the 461h Annual Technical Meeling 01 The Pelroleum Society 01 CiM in Banff, Alberta, Canada, May 14 ­17, 1995. Discussion of this paper is invited and may be presented at (he meeting if filed in wriling wfth (he technical program chairmanprior to the conclusion of the meeting. This paper and any discussion filed will be considered for publication in elM journals. Publicationrights are reserved. This is a pre-print and is sUbject to correction.

ABSTRACT

Horizontal drilling is a core technology for reservoirde:velopment. This paper is an overview oftoday's horizontaldrilling technology and a discussion ofhow the technologymay be used in the future, The following technologies will bediscussed:

Geosleeri1lg.

l'vlost horizontal If,.'el!s drilled today are placed in thereservoir based upon reservoir or geological parameters.MWD logging tools are being used to guide the well path asthe ...fell is being drilled This paper will discuss the variouslogging sensors available and how they can be used forgeosteering_

Underbalanced Drilling Systems

These systems are being developed to minimize formationdamage and ensure that the maximum production potentialofeach horizontal well is realized. Underbalanced drillingis being used primarily in pressure depleted reservoirs. Thispaper will review the different techniques being used anddiscuss the relative merits ofeach.

Multiple Lateral Wells.

These wells are being used to drain single reservoirs moreefficiently and to drain multiple reservoirs. Use ofmultiplelaterals can also reduce the number of sw1ace locations,which lessens environmental impact and reduces overallproject cost, The multiple laterals can be drilled using eitheropen hole sidetracks, or newly developed casing systems thatwill permit controlled reentry into each ofthe laterals. Thispaper presents an overview ofthe types ofwells being drilledtoday and discusses potential uses of the technology in thefuture

Short Radius Drilling Systems.

Short Radius Drilling Systems have been in use for manyyears. These systems have, however, had some significantlimitations. New systems have been developed which includeMWD tools for steering control, The development ofcomposite fibre drills/ring components will permit the use ofsteerable systems for drilling the horizontal interval. Thispaper discusses the potential uses of short radius systemsand how they will interface with other emergingtechnologies.

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These emerging technologies enhance the productioncapabilities of horizontal wells making them more effictivefor oil recovery than conventional vertical wells. In additionto improved recovery, field development costs are oftenreduced sinceftwer wells are required to drain the reservoir.The above emerging technologies will have an impact on the

number and type ofhorizontal wells drilled in the future.

INTRODUCTION

Until 1994, the number of horizontal wells drilled inCanada had approximately doubled each year (Figure I).For 1995, approximately 900 to 1000 horizontal wells willbe drilled, which is similar to the number drilled in 1994.

Most horizontal wells are development wells. When thenumber of horizontal wells drilled is compared to the numberof development wells drilled, we notice that horizonlal wellsare becoming a larger percentage of the development wells.This would tend to indicate that horizontal drillingtechnology is becoming or has become a core technology forreservoir development_

Horizontal Drilling Trends

The following horizontal drilling trends have beenobserved:

• an increase in build ratesa reduction in hole sizesan increase in re-entry drillingan increase in geosteering

The first three are related while the fourth is influenced bythe first three. The trend to use a higher build rate is basedupon a desire to minimize the measured length of the buildsection, minimize the vertical depth required to go fromvertical to horizontal, and to minimize the displacement fromthe spud point to the start of horizontal. If the displacementcan be minimized, the length of horizontal can be maximizedfor a given lease size. Since many operators have shown thatmore horizontal hole is better, there is a strong incentive tomaximize the length of horizontal interval for a given well.

The push to smaller hole sizes is the result of costoptimization and re-entry drilling. Most re-entries are from140 mm or 178 mm casing, so hole sizes are typically121 mm or 156 mm_ As experience was gained in drillingthese hole sizes, there was an increase in new drill wellsplanned with these hole sizes. Moving to smaller hole sizesreduces the cost of the well by using smaller cas iog andtubing and fewer consumables. Also, the move to open holecompletions has reduced the risks and concerns withcompletions in small diameter tubulars.

The move to smaller hole sizes permits the use of higherbuild rates since the small diameter tools are less stiff andcan be configured to achieve higher build rates. Forexample, the maximum build rate for 222 mm hole isapproximately 22°/30m while the maximum build rate for121 mm hole is approximately 45°/30m. Table I is asummary of the build rates achievable for a given hole size.

The trend to geosreering is something that has evolvedgradually since the first horizontal wells were drilled.Effective reservoir depletion using horizontal welts requiresoptimum placement of the wellbore within the reservoir.Recognition of this has resulted in more attention beingplaced on interpretation of geological parameters obtainedwhile drilling so that adjustments to the wellpath can bemade while the well is being drilled. Cuttings analysis andROP were the first parameters used for geosteering. Today.MWD logs are commonly used for geosteering. The usc ofthese logs for geosteering will be discussed brieny in anothersection.

HORIZONTAL DRILLING APPLICATIONS

The early horizontal wells were drilled primarily for oncof three reasons:

• to provide coning control• to intersect vertical fractures+ to increase reservoir exposure

While these continue to be the three primary applications,there have been significant changes to horizontal drillingtechnology that will have an impact on each of the aboveapplications. The application of horizontal well technologyhas also been impacted by the realization that reservoir.s aremuch more complex than what they were thought to be. Thesimple homogeneous reservoirs do not exist, or aL least arerare.

Horizontal drilling technology allows us to do manythings today that we could not do 5 years ago. Much of thiscapability is still developing, however it is possible Laspeculate on the impacts the technology will have on fULurereservoir exploitation. Horizontal drilling will enablecapture of reserves more efficiently and effectively thananyone imagined.

The Emerging technologies that will be discussed brienyare:

• geosteering• underbalanced drilling• multiple lateral wells

short radius drilling systems

Paper 95-03; Page 2