Formation Evaluation Workflow Assesses Mass-Transport Complex Reservoirs

2021 ◽  
Vol 73 (02) ◽  
pp. 63-64
Author(s):  
Chris Carpenter
Keyword(s):  
Mass Transport ◽  
Natural Fracture ◽  
Total Carbon ◽  
Nuclear Spectroscopy ◽  
Matrix Analysis ◽  
Abu Dhabi ◽  
Fast Neutrons ◽  
Formation Evaluation ◽  
Transport Complex ◽  
Pulsed Neutron

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203016, “Formation Evaluation in Mass-Transport Complex Reservoirs,” by Ulises Bustos, Schlumberger; Carlos Duran, Petróleos Sudamericanos; and Alvaro Chapellin, Schlumberger, et al., prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually from 9-12 November. The paper has not been peer reviewed. Mass-transport deposits (MTDs) are sedimentary, stratigraphic successions remobilized after initial deposition but before substantial lithification and transported downslope by gravitational processes as non-Newtonian rheological units. In the complete paper, the authors present an openhole advanced formation-evaluation approach that enables assessment of tight-matrix and natural-fracture systems at a level not previously accomplished in these types of geological formations. Introduction The considered wildcat project by Petroleos Sudamericanos is in the Lower Magdalena Valley hydrocarbon province in Colombia. From a stratigraphic point of view, the targets belong to tertiary deposits from the lower Neogene. Gravity-driven processes are complex and include creep, slide, slump, debris flow, and multiphase granular flows. The remobilized sedimentary deposits resulting from these processes are called MTDs or mass-transport complexes (MTCs) and are the main target job. Overlaying a crystalline basement, four MTC cycles were identified (although the present work only covers three MTC cycles) deposited in shallow marine environments. Each cycle consists of quartzite; phyllite; and schistose metamorphic rocks, largely gneiss with strong milonitization effects and foliated tremolitic marble in the top of the sequence. A summary of these types of rock is provided in the complete paper. The non-Archie nature of these rocks represents a challenge for formation evaluation. For reducing these uncertainties, a volumetric model with spectros copy dry-weight elements and nuclears was created that enabled solution of the total porosity, which was then benchmarked against the lithology-independent total nuclear magnetic resonance (NMR) porosity. The saturation computation was achieved with the fast neutron cross section method (FNXS) for the gas component and with total carbon for the liquid hydrocarbon fraction. The natural fracture system was analyzed with borehole image logs and with radial sonic-based dispersion analysis. The integration of matrix and natural-fracture assessment provided a robust formation evaluation that enabled identification of the main interest zones across the MTC cycles. Multifunction Spectroscopy for Matrix Analysis The multifunction spectroscopy tool is 1.72 in. in diameter and 18.3 ft long, consisting of a pulsed neutron generator and four detectors. The first detector is the compact neutron monitor, sensitive to fast neutrons and located adjacent to the high-output pulsed neutron source, measuring neutron output with high accuracy and precision. The second (near) and third (far) gamma-ray detectors are used for inelastic and capture spectroscopy measurements. The fourth and farthest-spaced detector (deep) uses an yttrium aluminum perovskite scintillator, which is involved in gas detection and assessment. The nuclear spectroscopy measurement is performed in energy and time domains; both aspects are described in detail in the complete paper.

Formation Evaluation in Mass Transport Complex Reservoirs

2020 ◽  
Author(s):  
Ulises Bustos ◽  
Carlos Duran ◽  
Alvaro Chapellin ◽  
Jose Araujo ◽  
Claudia Hincapie ◽  
...  
Keyword(s):  
Mass Transport ◽  
Formation Evaluation ◽  
Transport Complex

Khuff and Pre-Khuff Reservoir Fracture Characterization using the Cross Dipole Shear Wave Imaging and Borehole Imaging Data Integration

2021 ◽  
Author(s):  
Pradeep Menon ◽  
Tarek Swedan ◽  
Kamran Jan ◽  
M. S. Al-Shehhi ◽  
Piyanuch Kieduppatum ◽  
...  
Keyword(s):  
Imaging Technique ◽  
Complex Structure ◽  
Natural Fracture ◽  
Abu Dhabi ◽  
Destructive Interference ◽  
Acoustic Reflection ◽  
Reflection Imaging ◽  
Induced Fractures ◽  
Borehole Imaging ◽  
Acoustic Reflection Imaging

Abstract Increasing demands for gas in UAE have led to increased focus on more tight gas reservoirs like Khuff and pre-Khuff formations, away from the conventional oil-bearing carbonate reservoirs. The case study presented is in an offshore field, Northwest of Abu Dhabi city. The structure, with an area of 50 Sq.km was first identified in 1966 and it is part of the regional N-S extending structural. The multi-discipline approach applied in this study required the integration of a suite of open-hole data over a variety of length scales. Combination of the Borehole Acoustic Reflection Imaging technique and borehole imaging logs (BHI) in 3D, provides a better understanding of the complex fracturing network and the associated formation stress orientation up to 100ft away from the wellbore. The ability to "see" away from wellbore what was previously hidden on seismic, allows unlocking further potential reserves or avoiding certain production hazards. The well has penetrated the highly economical tight clastic Pre-khuff formation and the carbonate Kuff formation, allowing the analysis over a large geological history of offshore Abu Dhabi. The coherency of all data has helped establish for the first time a baseline understanding of the role of the fractures and fault in the petrophysical properties distribution along the wellbore and the 3D structural characterization in an larger area around the wellbore (up to 100ft). The emphasize in this paper is on the Borehole Acoustic Reflection Imaging technique (DSWI), which allows the identification of both intersecting and non-intersecting of geological features with a depth of investigation up to 100 ft away from the borehole. Moreover, the combination of DSWI with BHI have been used for the anisotropy estimation away from wellbore especially in a very tight and fractured reservoir deciphering multiple fault orientation, which potentially, cancel the anisotropy estimation due to destructive interference. In addition to the presence of drilling induced fractures interfering in with the natural fracture as seen on the BHI. The detailed BHI interpretation and the petrophysical data revealed that the fracture densities and orientation vary from bottom to top interval indicating tectonic regimes affecting the field. The lithological variation due to the evolution of the depositional setting has significantly influenced the fracture distribution and their length. The presence of these induced fractures and how deep they propagate into the formation, dominates the behavior acoustic anisotropy by reaching the flexural (dipole shear) investigation zone (3 to 4ft deep). It is also interesting to see the behavior of both natural and induced fractures and their respective strike change over the different formations revealing a geomechanically complex structure.

Predicting Hydraulic Fracturing in a Carbonate Gas Reservoir in Abu Dhabi Using 1D Mechanical Earth Model: Uncertainty and Constraints

2015 ◽  
Author(s):  
Manhal Sirat ◽  
Mujahed Ahmed ◽  
Xing Zhang
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Natural Fracture ◽  
Abu Dhabi ◽  
Hydraulic Fractures ◽  
Gas Reservoir ◽  
In Situ Stresses ◽  
Tight Carbonate ◽  
Different Depths

Abstract In-situ stress state plays an important role in controlling fracture growth and containment in hydraulic fracturing managements. It is evident that the mechanical properties, existing stress regime and the natural fracture network of its reservoir rocks and the surrounding formations mainly control the geometry, size and containments of produced hydraulic fractures. Furthermore, the three principal in situ stresses' axes swap directions and magnitudes at different depths giving rise to identifying different mechanical bedrocks with corresponding stress regimes at different depths. Hence predicting the hydro-fractures can be theoretically achieved once all the above data are available. This is particularly difficult in unconventional and tight carbonate reservoirs, where heterogeneity and highly stress variation, in terms of magnitude and orientation, are expected. To optimize the field development plan (FDP) of a tight carbonate gas reservoir in Abu Dhabi, 1D Mechanical Earth Models (MEMs), involving generating the three principal in-situ stresses' profiles and mechanical property characterization with depth, have been constructed for four vertical wells. The results reveal the swap of stress magnitudes at different mechanical layers, which controls the dimension and orientation of the produced hydro-fractures. Predicted containment of the Hydro-fractures within the specific zones is likely with inevitable high uncertainty when the stress contrast between Sv, SHmax with Shmin respectively as well as Young's modulus and Poisson's Ratio variations cannot be estimated accurately. The uncertainty associated with this analysis is mainly related to the lacking of the calibration of the stress profiles of the 1D MEMs with minifrac and/or XLOT data, and both mechanical and elastic properties with rock mechanic testing results. This study investigates the uncertainty in predicting hydraulic fracture containment due to lacking such calibration, which highlights that a complete suite of data, including calibration of 1D MEMs, is crucial in hydraulic fracture treatment.

An Integrated Study to Characterize and Model Natural Fracture Networks of Gas Condensate Carbonate Reservoirs, Onshore Abu Dhabi, UAE

2017 ◽  
Author(s):  
Budour Ateeq ◽  
Mohamed El Gohary ◽  
Khalid Al Ammari ◽  
Rashad Masoud ◽  
Abdelwahab Noufal ◽  
...  
Keyword(s):  
Gas Condensate ◽  
Carbonate Reservoirs ◽  
Natural Fracture ◽  
Abu Dhabi ◽  
Fracture Networks ◽  
Integrated Study

Formation Evaluation Using Advanced Pulsed Neutron Tools

2019 ◽  
Author(s):  
Abdulaziz Al-Qasim ◽  
Ilies Mostefai ◽  
Sunil Kokal ◽  
Abdulaziz AlKhateeb
Keyword(s):  
Formation Evaluation ◽  
Pulsed Neutron

Detection of Combined n/γ Fission Signatures Induced by an Epithermal Neutron Source

2017 ◽  
Vol 3 (3) ◽  
Author(s):  
A. Ocherashvili ◽  
T. Bogucarska ◽  
A. Beck ◽  
G. Heger ◽  
M. Mosconi ◽  
...  
Keyword(s):  
Neutron Source ◽  
Proper Time ◽  
Pulse Shape Discrimination ◽  
Fast Neutrons ◽  
Nuclear Materials ◽  
Test Assembly ◽  
Fission Neutrons ◽  
Pulsed Neutron ◽  
Prompt Fission ◽  
Multiple Detectors

In this paper, a method is presented for the detection of special nuclear materials (SNMs) in shielded containers, which is both sensitive and applicable under field conditions. The method uses an external pulsed neutron source to induce fission in SNM and subsequent detection of the fast prompt fission neutrons. The detectors surrounding the container under investigation are liquid scintillation detectors able to distinguish gamma rays from fast neutrons by means of pulse shape discrimination method (PSD). One advantage of these detectors, besides the ability for PSD analysis, is that the analog signal from a detection event is of very short duration (typically few tens of nanoseconds). This allows the use of very short coincidence gates for the detection of the prompt fission neutrons in multiple detectors, while benefiting from a low background coincidence rate, yielding a low detection limit. Another principle advantage of this method derives from the fact that the external neutron source is pulsed. By proper time gating, the interrogation can be conducted by epithermal source neutrons only. These neutrons do not appear in the fast neutron signal following the PSD analysis, thus providing a fundamental method for separating the interrogating source neutrons from the sample response in the form of fast fission neutrons. This paper describes laboratory tests with a configuration of eight detectors in the Pulsed Neutron Interrogation Test Assembly (PUNITA). Both the photon and neutron signature for induced fission is observed, and the methods used to isolate these signatures are described and demonstrated.

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