Microseismic Fracture Mapping Optimizes Development of Low-Permeability Sands
Notice bibliographique
Résumé
This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 95637, "Microseismic Fracture Mapping Optimizes Development of Low-Permeability Sands of the Williams Fork Formation in the Piceance Basin," by S.L. Wolhart, SPE, Pinnacle Technologies; C.E. Odegard, SPE, Williams Production; and N.R. Warpinski, SPE, C.K. Waltman, SPE, and S.R. Machovoe, SPE, Pinnacle Technologies, prepared for the 2005 SPE Annual Technical Conference and Exhibition, Dallas, 9–12 October. A study was made to improve hydraulic fracturing and field development in the Williams Fork formation, Piceance basin, Colorado. Wells in this formation usually are stimulated in multiple stages by use of limited-entry techniques. Microseismic imaging was used to assess well downspacing and to assist stimulation optimization. Introduction Microseismic mapping was performed on a four-well project during the winter of 2001–02. The mapping improved the understanding of well placement and fracture optimization for a large pilot project evaluating 10-acre well spacing in the field. The goals of the mapping were to determine fracture orientation and dimensions (height and half-length) as well as the treatment distribution in these fields. Background As shown in Fig. 1, the Williams Fork formation is part of the Mesaverde group and consists of many stacked low-permeability sandstones. Gross formation thickness can exceed 2,000 ft. These low-permeability sandstones have porosities ranging from 6 to 14% and matrix permeability ranging from 0.1 to 5.0 µd. All intervals are naturally fractured to some extent, and effective permeability is 10 to 50 µd. Natural fractures terminate at lithologic boundaries and do not connect layers vertically. Layers are limited in lateral extent, and there is little or no correlation of intervals between wells even with reduced well spacing. Gas in place averages 40 to 100 Bcf per 640-acre section. Estimated ultimate recovery is 1.3 to 1.7 Bcf/well in core areas. The recovery factor for wells on 20-acre spacing is approximately 40%, and for 40-acre spacing it is approximately 20%. At the time of this testing, the fields were developed primarily on 20- to 40- acre well spacing. Stimulation Practices Hydraulic fracturing is required to sustain commercial production from these low-permeability reservoirs. Fracture treatments usually are in multiple stages with limited-entry procedures. Each fracture stage targets three to six sands. Early treatments used crosslinked-gel fluid. Beginning in 2001, some wells were stimulated with waterfracs. Typical waterfrac designs consisted of 80,000 to 140,000 gal of slickwater plus 90,000 to 160,000 lbm of 20/40-mesh Ottawa sand pumped at 40 to 50 bbl/min. Typical gel fracture-treatment designs consisted of 60,000 to 140,000 gal of 30-lbm/1,000-gal crosslinked gel plus 300,000 to 700,000 lbm of Ottawa sand pumped at 40 bbl/min. Stages covered gross intervals of 300 to 500 ft with four to six sets of perforations. Both the waterfracs and gel fracture treatments were limited-entry designs with 18 to 20 total perforations. Average sand concentration was 1.2 lbm/gal for the waterfracs and 5.0 lbm/gal for the gel fracture treatments.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».