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CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Vol. 39 (1991), No. 3. (September), Pages 233-251

Previous HitReservoirNext Hit Quality Evaluation from Visual Attributes on Rock Surfaces: Methods of Estimation and Classification from Drill Cuttings or Cores

Valerie G. Ethier, Howard R. King

ABSTRACT

Skill in the accurate prediction of permeability (as well as Previous HitporosityNext Hit) is developed from 1) an understanding of the most important determinants of permeability and 2) reference to analyzed rock which is comparable in Previous HitreservoirNext Hit quality. The following factors have direct influence on permeability in rocks: grain size and shape, sorting, and consolidation (cementation and compaction). These affect pore and pore throat size and shape. Factors that are less well understood but that also influence permeability are surface areas and microporosity. All of these elements need to be considered. Some are not as easily quantified as others using a stereomicroscope, so require more practice. The ability to predict both Previous HitporosityNext Hit and permeability from cuttings has application not only in well-site work but also in prospect evaluation and in well-completion decisions.

In this paper, we illustrate methods of Previous HitreservoirNext Hit quality evaluation for siliciclastics comparable to those developed for carbonates by Archie (1952) and Lucia (1983). Our methods start with a textural assessment of the broken surface for relief, consolidation, grain size and the abundance of clays. These concepts were developed by Sneider et al. (1983) and Sneider and King (1984). This textural information is then used in a graph to predict unseen Previous HitporosityNext Hit. An estimate of visible Previous HitporosityNext Hit plus the unseen Previous HitporosityNext Hit gives total Previous HitporosityNext Hit. A grain size-total Previous HitporosityNext Hit graph is used to predict permeability.

The results of Previous HitreservoirNext Hit quality estimation methods, whether for siliciclastics or carbonates, may be combined within a scheme which assigns rocks to one of five categories (labelled SR-1 to SR-5) based on permeability. This Previous HitreservoirNext Hit-quality scheme coexists with, and is in addition to, textural or facies classifications because it gives us information on Previous HitreservoirNext Hit attributes of the rock rather than on its origin.

RESUME

L'art de predire correctement la permeabilite (ainsi que la porosite) est developpe a partir 1) d'une comprehension des facteurs les plus importants de la permeabilite et 2) de la comparaison a des roches analysees de qualite de Previous HitreservoirNext Hit similaire. Les facteurs suivants ont une influence directe sur la permeabilite des roches : taille et forme des grains, classement, et consolidation (cimentation et compaction). Ceux-ci affectent la taille et la forme des pores et des goulots de pores. La surface des grains et la microporosite sont des facteurs qui sont moins bien compris mais qui influencent egalement la permeabilite. Tous ces elements doivent etre pris en consideration. Certains d' entre eux ne sont pas aussi facilement quantifies que d' autres en utilisant un stereomicroscope, et recquierent donc plus de pratique. La capacite de predire a la fois porosite et permeabilite a partir de deblais de forage s'applique non seulement aux taches de chantier de forage mais aussi a l' evaluation des zones d' interet et aux decisions de completion de puit.

Dans ce papier, nous illustrons des methodes d'evaluation de qualite de Previous HitreservoirNext Hit pour sediments siliciclastiques comparables a celles developpees pour carbonates par Archie (1952) et Lucia (1983). Nos methodes commencent par une evaluation texturale du relief, de la consolidation, de la taille des grains et de l'abondance d'argiles, a partir de la surface brisee. Ces concepts furent developpe par Sneider et al. (1983) et Sneider et King (1984). Cette information texturale est ensuite projetee dans un graphique afin de predire la porosite invisible. Une estimation de la porosite visible ajoutee a la porosite invisible donne la porosite totale. Un graphique reliant la taille des grains a la porosite totale est utilise pour predire la permeabilite.

Les resultats de methodes d'estimation de qualite de Previous HitreservoirNext Hit, que ce soit pour sediments siliciclastiques ou pour carbonates, peuvent etre combines dans un systeme qui assigne aux roches l'une des cinq categories (appelees SR-1 a SR-5) basees sur la permeabilite. Ce systeme de qualite de Previous HitreservoirNext Hit coexiste avec, et est un complement des classifications texturales et de facies parce qu'il nous informe des caracteristiques de Previous HitreservoirTop de la roche plutot que de son origine.

Traduit par Patrice de Caritat

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