Sonatrach

About: Sonatrach is a company organization based out in Algiers, Algeria. It is known for research contribution in the topics: Hydraulic fracturing & Structural basin. The organization has 460 authors who have published 494 publications receiving 6339 citations. The organization is also known as: Sonatrach SPA.

New Methods for Estimating of Formation Pressures and Fracture Gradients from Well Logs

Abstract: The accurate prediction of pore pressures and fracture gradients has become almost essential to the drilling of deep wells with higher than normal pore pressures. Drilling costs and problems can be reduced substantially by the early recognition of abnormally high pore pressures. Two new methods have been developed from well logs that can be applied universally to the determination of pore pressures and fracture gradient. The first method uses the principle of compaction concept where the porosity varies exponentially with vertical stress, and the second method uses the power-law relationship. Acoustic logs obtained from five wells in Ouargla and Garet El Bouib fields are used to validate the two methods. The computed pressures matched the measured pressures obtained from repeated formation tests (RFT). The deviation between the first method and RFT varies from 3% to 6%, while, the deviation for the second method varies from 1% to 3%. The acoustic log predicts fluid pressure within an accuracy of 0.05 psi/ft. The standard deviations for the first method and the second method are 0.04 psi/ft and 0.02 psi/ft respectively. The analysis also shows that there are two overpressured zones in the well studied, which accurately matched the actual sequence of events while drilling the wells. The developed methodologies are illustrated and validated with several examples from the Hassi Messaoud field in Algeria.

Parameters controlling the quality of the Hamra Quartzite reservoir, southern Hassi Messaoud, Algeria: insights from a petrographic, geochemical, and provenance study

Abstract: Petrographic and geochemical analysis of the Hamra Quartzite reservoir in the southern periphery of the Hassi Messaoud field has been undertaken The aim is to identify the quality of these sandstones as well as their tectonic setting and possible provenance Petrographic analysis reveals that the studied reservoir is constituted of fine- to coarse-grained sandstones in which quartz forms the principal framework mineral The main cement phases identified in this reservoir are quartz, illite, and carbonate, precipitated in that order The principal diagenetic factors controlling the reservoir quality are quartz overgrowths, formation of authigenic clays, and the precipitation of carbonate cement The Hamra Quartzite reservoir is considered mature from a compositional point of view as it consists predominantly of quartz arenites Geochemically, these sandstones have a high SiO2 content (9328–9879 wt%) The Hamra Quartzite deposits appear to be derived from deeply weathered (under warm–humid climate conditions) granitic–gneissic terrains or recycled sedimentary source areas A passive margin origin is the most likely tectonic setting for the depositional environment of these arenites The reservoir quality is strongly influenced by the relationship between the clay content and mineralogy The combined effect of quartz overgrowth and the plugging of pores by illite have reduced both porosity and permeability As a result, economically viable oil production in this area will depend most strongly on the combination of matrix and fracture porosity