Carbonate reservoirs are commonly heterogeneous and their reservoir quality results from complex interactions between depositional facies and diagenetic processes. The Diagenetic Diagram is a powerful tool that helps in the characterization of the diagenetic processes that have affected the reservoir. From this knowledge, it is possible to significantly improve the understanding of the reservoir's pore system and permeability distributions, which are key factors for development optimization and production sustainability.
A multi-scale and multi-method study (petrography, blue-dye impregnation, selective staining and porosity determination) of Middle Jurassic carbonates from the Lusitanian Basin (Portugal) has been undertaken, to find the best systematic approach to these reservoirs. It has involved thorough diagenetic characterization of each lithotype (lithofacies, texture, porosity, qualitative permeability assessment and diagenetic evolution). The study area was selected based on its excellent and varied exposures of carbonate facies and availability of core.
Methodological and terminological challenges were faced during the study, especially dealing with data coming from several scales (macro, meso, and micro). In order to overcome these challenges, a diagenetic diagram was developed and applied to the selected rocks. It is a tool that allows the integration of data coming from outcrops, hand samples, cores, cuttings, thin sections, and laboratory experiments.
This is carried out in a dynamic, guided, systematic, and rigorous way, enabling the evaluation of the relationship between facies, diagenetic evolution and pore systems. The latter are characterized regarding size, geometry, distribution, and connectivity. This enables the identification and characterization of permeability heterogeneities in the rocks. It was concluded that the main porosity class (i.e. secondary) was created by diagenetic processes.
The proposed method has strong application potential for: detailed characterization and understanding of porosity and permeability in carbonate reservoirs, from a diagenetic evolution and fluid flow perspective (e.g. SCAL and pore system description); definition of diagenetic trends for modeling petrophysical properties and rock types. In this regard, the method is being applied to a Valanginian carbonate reservoir in Kazakhstan, and some preliminary results are presented in this paper. Refining this technique may be helpful for similar carbonate studies, enhancing the results of typical diagenetic studies by improving the characterization of reservoir properties at various scales, thus contributing to a more sustainable exploitation of hydrocarbon reservoirs.
The post-Macondo response has included new regulations, new industry standardsand new recommended practices such as API RP96, BUL 97 and the Workplace SafetyRule (per the existing RP75) for Offshore Safety and Environmental Management(SEMs). These are nominally cross referenced, but it is still not clear whatholds them together and makes them work as a "system" for well design,construction and operation. Furthermore, there are inherent interface issuesbecause RP96 deals across different phases of the project delivery process(well design and construction), while BUL 97 and RP75 cover differentparticipants (contractor/operator). The theme of this paper how to deal withthe two issues of systematic integration and interfaces using the bow-tiesystem.
Even though well design and construction project participants may havediffering commercial and cultural perspectives, they all have an interest inavoiding major accident events. Implementing and maintaining barriers supportsthis interest. This paper discusses an analysis of how barriers,contractor/operator bridging documents and safety and environmental managementplans have worked or not worked in 28 different offshore well controldisasters. It will also show how the bow-tie system can improve riskcommunication by providing a "lingua franca" between the various projectparticipants and at different phases of the project. The lessons from thesecase studies will offer a path forward for the industry to successfullyimplement post-Macondo requirements based upon API RP96, BUL97, SEMs and otherreference standards dealing with Major Accident Events offshore.
Post-Macondo Developments in Barriers, Bridging Documents and SEMs
The response to the April 2010 Macondo disaster by the oil and gas industryincludes new oil and gas regulations, recommended practices and guidelines.Among these are two draft (as of January 2012) American Petroleum Institute(API) publications: API RP96, BUL 97 and the 2010 US Workplace Safety Rule(which incorporates API RP75 by reference) . In this paper I will refer tothese as "standards" a generic sense, in that I expect them all to becomestandard practice for oil and gas operations in the US GoM over the comingyears.