Estimating Cementation Factor (m) for Carbonates Using Borehole Images and Logs

Abstract

Carbonate reservoirs account for 60% of today's hydrocarbon production. Several giant carbonate fields in the Middle East are expected to be the dominant source of hydrocarbon production through the current century. Therefore, understanding carbonate reservoirs and producing them efficiently have become industry priorities and are likely to remain so. In order to assess a possible hydrocarbon reservoir, hydrocarbon saturation needs to be determined with good accuracy. In 1942 Archie published a formula to estimate water saturation in reservoirs. In case of carbonates, the saturations computed by the formula are not always correct. The factors complicating the role of the formula are known as Archie Exponents, namely, porosity exponent (m, also known as cementation factor) and saturation exponent (n). Both exponents tend to vary quite often in the carbonate reservoirs. With the exception of cores, no reliable and well established techniques exist today that can give a good estimate of these exponents. Estimating cementation exponent (m, porosity exponent) from the well logs is the main objective of this paper. The technique addressed in it is based on the assumption that the amount and pattern of cementation, caused by diagenesis, in carbonates is one of the factors controlling the value of m. Therefore in order to estimate it for carbonates, the cementation in them should be quantified. It was achieved through integration of electrical borehole images and petrophysical logs with the cores. The data on cementation was then used to estimate 'm' as a continuous curve for carbonate reservoirs. The technique provides a unique way, which incorporates textural part of carbonates, to estimate cementation factor (m) for carbonates. It has been applied to carbonates of the Middle East and Europe with good results, which were verified by the core data and production results.

Quantitative diagenesis: Methods for studying the evolution of the physical properties of tight carbonate reservoir rocks

“…It is estimated that approximately half of all known global oil reserves occur in carbonate rocks. Furthermore, carbonate reservoirs provide nearly half of current hydrocarbon oil and gas production (Ramakrishnan et al, 2001;Akbar et al, 2008;Barros-Galvis, 2018). Carbonates are the dominant reservoir type in the Middle East (Hollis, 2011;Al-Qayim and Rashid, 2012;Al-Qayim and Othman, 2015;Hollis et al, 2017;Jafarian et al, 2017;Adam et al, 2018;Aldega et al, 2018;Bigi et al, 2018) and this region contains nearly 15% of the world hydrocarbon reserves (Normi and Standen, 1997).…”

Coquinas da Formação Itapema, Campo de Mero (Pré-sal da Bacia de Santos): Análise de Microfácies e Paleoambiente Deposicional

“…O estudo de rochas carbonáticas destaca-se pelo fato de constituírem-se em reservatórios com expressivos volumes de hidrocarbonetos (Kinoshita, 2010), as quais são responsáveis por aproximadamente 50% das reservas mundiais (Ramakrishman et al 2001) e cerca de 60% da produção no mundo (Akbar et al 2008).…”

Petrophysical Evaluation of a Severely Heterogeneous Carbonate Reservoir; Electrical Image Logs Usage in Porosity Estimation

“…Classification and clustering methods were used by some of the authors to estimate permeability from image logs [16] [17]. Also, cementation factor (m) was estimated as a continuous curve from borehole images and petrophysical logs [18] and shale volume calculated using binarization technique by electrical image logs [19]. Furthermore, in some studies it was attempted to separate and calculate vuggy porosity using electrical image logs [20] [21].…”