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 GCPrevious HitFractureNext Hit Models and Fractured Reservoirs*

By

Steve Ahlgren1, Jim Holmlund2, Paul Griffiths1, and Rob Smallshire1

 

Search and Discovery Article #40100 (2003)

 

*Adapted for online presentation from the Geophysical Corner column in AAPG Explorer September, 2002, entitled “Previous HitFractureNext Hit Model Previous HitAnalysisNext Hit Is Simple,” prepared by the authors. Appreciation is expressed to the authors, to R. Randy Ray, Chairman of the AAPG Geophysical Integration Committee, and to Larry Nation, AAPG Communications Director, for their support of this online version. 

EDITORIAL NOTE: The reader is referred to a companion article, entitled “Using 3-D Outcrop Laserscans for Previous HitFractureNext Hit Previous HitAnalysisNext Hit,” prepared by authors Ahlgren and Holmlund.   

1Midland Valley Exploration, Glasgow, UK ([email protected])

2Geo-Map Inc., Tucson, Arizona

 

Introduction 

Ahlgren and Holmlund (2003) describe a new Previous HitfractureNext Hit detection method incorporating a portable laserscan unit to completely image analog outcrops in three dimensions. In this article, we explore how simple Previous HitanalysisNext Hit of calibrated analog Previous HitfractureNext Hit models can enhance exploration and production in fractured reservoirs. 

After collecting laserscan data from analog outcrops, semi-automatic processing extracts important Previous HitfractureNext Hit data such as geometries, intersections, trace lengths and orientation statistics. These statistical and spatial properties are extrapolated in three dimensions and used to generate synthetic Previous HitfractureNext Hit models at a scale consistent with existing or planned wells. The synthetic, three-dimensional Previous HitfractureNext Hit networks have similar statistical and topological characteristics of observed data, but offer distinct advantages over their natural counterparts. One important benefit is the ability to construct multiple realizations of the observed fractures quickly to test different hypotheses and perform sensitivity testing of the input parameters. Results also can be compared to well production volumes and modified to get good matches.

 

 

uIntroduction

uFigure captions

uTechnique

uConclusion

uReference

uAcknowledgment

 

 

 

 

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

uIntroduction

uFigure captions

uTechnique

uConclusion

uReference

uAcknowledgment

 

 

 

 

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

uIntroduction

uFigure captions

uTechnique

uConclusion

uReference

uAcknowledgment

 

 

 

 

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

uIntroduction

uFigure captions

uTechnique

uConclusion

uReference

uAcknowledgment

 

 

Figure Captions

Figure 1. Meshed laserscan image of a fractured outcrop on Mt. Lemmon, Ariz. The face measures 28m x 18m.

 

Figure 2. Synthetic Previous HitfractureNext Hit model with proposed well. The model contains four Previous HitfractureNext Hit sets interpreted from the laserscan data. A synthetic, deviated wellbore intersects the Previous HitfractureNext Hit network at the upper right side of the figure.

 

Figure 3. The synthetic well drains four distinct fractured volumes.

 

 

 

Figure 4. Changing the mean length and aspect ratio of one Previous HitfractureNext Hit set yields significant changes in the volume of one of the intersected components.

 

 

Click to view in sequence the differences in the model, as illustrated by Figures 2, 3, and 4.

 

Technique 

The new laserscan technique provides robust statistical data on Previous HitfractureNext Hit orientations, clustering and, to a lesser degree, Previous HitfractureNext Hit spacing. Parameters such as Previous HitfractureNext Hit trace length and shape (i.e., aspect ratio) also may be extracted from the laserscan data using techniques such as trace Previous HitanalysisNext Hit, but with lesser certainty. Constructing multiple Previous HitfractureNext Hit networks using different parameters and analyzing them with a few simple tools may help to determine the relative importance of these less-constrained parameters. More importantly, the simple Previous HitanalysisNext Hit may indicate whether a more detailed Previous HitfractureNext Hit investigation is truly necessary. 

One technique is three-dimensional connectivity Previous HitanalysisNext Hit, which determines how well connected or poorly connected fractures are within a natural or synthetic network. Parameters such as Previous HitfractureNext Hit volume and Previous HitfractureNext Hit area are extracted and may be useful for Previous HitfractureNext Hit modeling or well planning. Often, wells that intersect different components cannot communicate with one another, so defining the likely extent and volumes of the components is critical in making production estimates. For example, consider a simplified synthetic Previous HitfractureNext Hit network generated using orientation and length data extracted from a laserscan of a ~500m2 outcrop face (Figure 1). 

  • Orientation data are extracted by orientation cluster Previous HitanalysisNext Hit.

  • The Previous HitfractureNext Hit length distribution is estimated using two-dimensional trace Previous HitanalysisNext Hit. In this example, the length and aspect ratio (Previous HitfractureNext Hit length divided by Previous HitfractureNext Hit height) of the fractures are less constrained than other key parameters, reflecting a commonly encountered situation in three-dimensional Previous HitfractureNext Hit modeling.

 

The resulting scale model of the Previous HitfractureNext Hit network contains four Previous HitfractureNext Hit sets, each with a similar statistical signature as those interpreted from the outcrop laserscan data (Figure 2). A synthetic well is “drilled” into the model and used as the basis for connectivity Previous HitanalysisNext Hit. The Previous HitanalysisNext Hit quickly reveals that the well intersects a number of Previous HitfractureNext Hit clusters with relatively small drainage volumes (Figure 3). 

Since the Previous HitfractureNext Hit lengths and aspect ratios are not uniquely defined, sensitivity testing of this Previous HitfractureNext Hit model might include changing the aspect ratio and lengths of one or more of the Previous HitfractureNext Hit sets, and re-analyzing the model for connectivity. To this end, a new model is constructed using one Previous HitfractureNext Hit set with twice the length and aspect ratio as in the first model. Connectivity Previous HitanalysisNext Hit shows that the model is indeed sensitive to these changes, as reflected by the difference in drainage volumes intersected by the synthetic well (Figure 4). 

Although both Previous HitfractureNext Hit models contain three primary drainage volumes of roughly equal size, the second model contains one volume (colored in yellow) almost 500x larger than in the first model. If the actual production volume for the well were known, it would be essential to compare these data with the new model to determine if a more detailed assessment of Previous HitfractureNext Hit size is important.

 

Conclusion 

Laserscanning can be used to generate calibrated Previous HitfractureNext Hit models that enhance the understanding of a fractured reservoir. Models can be built around existing or proposed wells, and analyzed with simple techniques such as connectivity Previous HitanalysisNext Hit. 

Sensitivity testing may help to provide additional confidence in well planning and the Previous HitfractureNext Hit network interpretation.

 

Reference 

Ahlgren, Steve, and Jim Holmlund, 2003, Using 3-D outcrop laserscans for Previous HitfractureNext Hit Previous HitanalysisTop: Search and Discovery Article #40099 (2003).

 

Acknowledgment 

This research was funded in part by BP.

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