Clay shale landscapes are sensitive to landslide, erosion, and re-sedimentation processes. In this context, tectonized clay shales have peculiar hydrological and mechanical behaviours. In order to improve our understanding of the processes involved in such systems, an experimental site has been settled in the Draix Observatory (ORE DRAIX) on a black marl hill slope of the Southern Alps (France) in the framework of the ECOU-PREF project. The site is a natural laboratory to study the evolution of clay shale landscapes at several scales (regional to µm). In this study, we aim to characterize the internal structure and fissure patterns of a stable interfluve, in order to locate preferential water flows within the system, and anticipate its evolution. This work is based on a series of mutli-disciplinary approaches including petrophysical analyses, well pulse injection tests and downhole geophysical measurements. Borehole geophysical results were combined with laboratory measurements on core plugs (permeability, density, porosity, and acoustic velocity). Optical and acoustical images have been used as an original tool for internal discontinuities characterisation and potential active flow path detection. They allowed the identification of three main lithological units interpreted as several stages of shale alteration. In addition, several main structural plane discontinuities (open fractures, schistosity planes, and fractures infilled with calcite or clays) were identified from the images and their potential transmissivity discussed with regard to piezometric and tracer measurements. In all, the integration of measurements leads to propose a simple scenario of fluid circulation and chemical alteration of the interfluve

While traditional mudlogging techniques provide largely qualitative data, the prime objective of Advanced Mud Logging (AML) is to provide quantitative real time measurements in aid of a complete formation evaluation. To achieve this, wellsite mudlogging technologies have been enhanced, and various techniques which historically were limited to laboratories, have been adapted for well site usage. AML well site techniques thus include: (1) high frequency, improved accuracy monitoring of drilling parameters; (2) enhanced cuttings image acquisition and processing; (3) direct measurements on cuttings, including graindensity, spectral GR, NMR, XRD, XRF; and (4) sophisticated mud gas analysis capabilities.We describe the main system components developed and present some results of the first pilot tests done in Saudi Arabia with AML techniques and a dedicated AML unit. Examples in the four areas mentioned above illustrate and confirm the potential of AML. On one special technology test well, different systems, from two different companies, were run in parallel to establish the merits and possible limitations of especially the hydrocarbon analysis systems.One of the most striking examples of the quality of AML is a perfect match between the hydrocarbon fluid composition determined from mud gas returns, and those subsequently obtained from PVT measurements on wireline fluid samples. To achieve this, AML technology developers in the industry advanced across the whole process chain affecting such quantification. First and foremost, improving sample extraction and handling, combined with enhanced calibration procedures, to convert from in situ to surface conditions. Second, in addition to sampling both the return mud flow and the inflow, a more precise tracking of flowrates and system volumes was made possible with modern operating systems. Third, adding a mass spectrometer to the gas chromatograph, improved the final measurement potential. Introduction.Several years ago, in Saudi Aramco, a clear business need emerged for additional petrophysical techniques in cases where traditional formation evaluation technologies were unable to provide all the necessary answers with sufficient certainty. Interpretation of tight gas formations in particular was challenging, because the formation properties typically were right at the edges of the operating envelopes of normal logging tool measurements and interpretation technology. With a perceived potential for AML technologies to aid in several of those challenges, an AML research area was set up. The mission was to expand and improve existing mudlogging technologies, and introduce and develop new ones. The vision had two related, but distinct elements. Firstly, also labeled as "ARCHIE'S DREAM" 1 , a complete, albeit preliminary, as a "first aid", formation evaluation, based solely on AML data, including mineralogy, fluid contacts and fluid characterization, porosity and even saturation, permeability and other parameters normally derived from conventional electric logging and cori...

No abstract

While traditional mudlogging techniques provide largely qualitative data, the objective of Advanced Mud Logging (AML) is to provide quantitative real time measurements and information in aid of drilling and a complete formation evaluation. Hence, during the past few years, various techniques which before were limited to laboratories, have been adapted for well site usage. Also, the whole surface logging system, from sensors to computer operating systems, have been enhanced. A systematic comparison of results between laboratory instrument and field version instruments proved that the quality of results does not need to be given up when applying these techniques at the wellsite. At present AML well site techniques thus include (i) enhanced monitoring of drilling parameters, (ii) sophisticated mud gas analysis capabilities, (iii) enhanced cuttings image acquisition and processing, and (iv) several direct petrophysical measurements on cuttings. We present some results of several field tests done in Saudi Arabia with a dedicated AML unit, where all these new techniques have been integrated. In this unit, next to conventional techniques, such as calcimetry, measurements on cuttings include X-ray diffraction (XRD), X-ray fluorescence (XRF), Nuclear Magnetic Resonance (NMR), spectral GR, grain density and porosity. Examples in each of the four areas mentioned above confirm the potential of AML. AML mud gas analysis gives quantitative compositional HC analysis which perfectly matches results from PVT tests done on subsequent wireline fluid sampling. Also: while the depth resolution of mudlogging measurements, typically several feet, is less than of especially wireline logging, normally sampled at half foot increments, the latest AML NMR measurements have the potential for very high resolution measurements, making it possible to establish the petrophysical properties of very thinly laminated sequences, where normally neither conventional wireline logs nor core plug measurements can resolve those.