by Gulfiia Ishmukhametova, NAM
After initial plug and abandonment activities in one reservoir, measurements showed pressure build up in the annuli. Spectral noise, high precision temperature and production logging were performed to determine the cause of sustained annulus pressure and the location of leaks. The data acquisition was performed both under shut-in and pressure bleed-off conditions and both log responses were compared to identify changes in noise patterns. The noise from specific events such as channeling or reservoir activity was detected, so the abandonment program could remediate these issues successfully.
Application of spectral noise logging in this field yielded evidence that this technology can identify annulus flow for very minor build-up rates (0.1 bar/day). Our work demonstrates the ability to locate the source behind multiple barriers and to validate plug integrity. It was observed that noise responses have a good correlation with ultrasonic cement evaluation logs aiding better understanding of the gas migration mechanism and change in noise patterns.
by Kamaljeet Singh – Schlumberger
Worldwide, government and regulatory officials are informing the oil & gas industry that unproductive wells must be sealed to permanently remove these potential environmental threats. Services companies are developing tools and methods to limit the economic impact of fulfilling these obligations. A crucial requirement of permanent abandonment procedure is the placement of a cement plug across the wellbore and in the annuli of remaining casing sections in the well once upper sections have been successfully cut and pulled out.
This presentation aims to demonstrate the use of a multi sensor wireline tool to characterize annular material based on acoustic impedance properties and flexural wave imaging. This data is used to confirm annular barrier, support casing cut and pull optimization and evaluate Perforate, Wash & Cement (PWC) P&A technique.
Data acquisition is an essential part of the exploration and development phase of a project. Data has its highest value when obtained in the exploration phase of a project where the aim is to reduce uncertainties as much as possible. Due to the low oil price many exploration projects are cancelled or deferred. Those projects which are approved are challenged with keeping the costs as low as possible.
EBN is in the unique position to see the trends of data acquisition in the recent years and the value of the information taken from data acquisition. To emphasize these trends a data analysis is done on almost 20 exploration wells of the past 5 years. Since EBN is partner in almost all oil and gas wells in the Netherlands, it has a great overview of the logging strategies of the operators and their post-mortem challenges. Hence EBN is encouraging a basis set of logging measurements in exploration wells as a best practice for the Dutch Oil and Gas industry.
Value of information analysis impact on data acquisition programs
by Jean-Paul Koninx, Shell
In a time of lower oil prices and cost reductions, data acquisition programs are under pressure. They are an easy target for quick cost cutting. How to safeguard essential data acquisition? How to assess the value of it?
The answer lies in a structured Value of Information analysis. While there are a lot of misconceptions and myths around VOI analyses, the presenter will provide you with a simple and structured approach, that can be easily applied to many problems. This not only helps justify your data acquisition (if warranted!), but in fact brings out where the value is.
System Approach for Enhanced Pulsed-Neutron Applications
Jon Musselman (Weatherford)
Through-casing formation evaluation using pulsed-neutron measurements has advanced to address many challenging environments. Relatively low porosity, multiple casing strings, complex completion hardware, and the need for very accurate fluid saturation results are a few of many situations that pose challenges for traditional capture measurements with conventional pulsed-neutron tools. These challenges can be met using a systems approach. Advanced tool hardware and instrumentation forms the foundation of the logging system, but a combination of rigorous calibration, detailed response characterization, and powerful workflows and analysis techniques are required for accurate results.
The presentation reviews one such system, with emphasis on the response characterization and summary workflows derived from characterization. These can be applied to oil and gas reservoirs in a wide range of environments.
Extended Monitoring of a Mature Field – A Case Study
Hans de Koningh (Xodus Group)
A mature gas field changed ownership after 30 years of production. The field produces from multiple fault compartments, with varying gas – water contacts and depletion mechanisms. The new owner resumed field surveillance with a large campaign including several pulsed neutron log surveys. ON interpretation of the data it was found that many of the new surveys deviated significantly and consistently from original baseline surveys. An explanation was found to explain these deviations and justify a correction so that the entire set of pulsed neutron surveys could be interpreted consistently.
Joint Interpretation of Magnetic Resonance- and Resistivity-Based Fluid Volumetrics – A Framework for petrophysical evaluation
Holger Thern (presenter) and Geoffrey Page, Baker Hughes
The accurate quantification of fluid volumes is one of the most important tasks for determining the economic value of hydrocarbon reservoirs. Fluid saturation calculation from resistivity logging data has been established for many decades with known benefits and challenges. More recently, the nuclear magnetic resonance (NMR) logging technology has developed as an alternative, robust method for direct fluid volume estimation by separating movable from bound fluids. As today’s reservoirs are becoming more challenging, conventional resistivity logging data evaluation involves increasing difficulties and ambiguities, for instance in complex lithology due to the presence of conductive minerals, low formation water salinity, fractures and vugs, or local variations in water resistivity. NMR logging data processing and interpretation are also not straight-forward in complex carbonates and heavy oil reservoirs, as well as in case of wettability alteration and due to the presence of magnetic minerals. Ambiguities in either of the measurements can be efficaciously addressed by combining data from both logging services.
We present a systematic compilation and discussion of main properties affecting resistivity and NMR fluid volume estimations such as Archie parameters and T2 cutoffs. Several log examples illustrate a wide range of reservoir scenarios. In addition to the log interpretation aspect, we also relate the results to their applications ranging from real-time drilling optimization through hydrocarbon-in-place estimates and reservoir modeling input to production and completion decisions.
Forward Modelling of NMR Logs in a Chalk Reservoir
Wim Looyestijn (consultant)
It is well known that interpretation of NMR logs on the basis of core-derived parameters often fails because the down-hole situation is much different from that in the laboratory. Core measurements at full in-situ conditions are in principle possible, but very expensive and therefore bound to span a limited range of properties.
We demonstrate that the same can be achieved by forward modelling of the NMR response. Starting point is a representative set of water-saturated core samples measured at ambient conditions. Forward modelling then introduces changes in the NMR response corresponding to full in-situ conditions, including effects due to the presence of native hydrocarbons, mud filtrate invasion and wettability. Interpretation parameters, such as (variable) T2-cutoff, and permeability exponents can now be computed on NMR data as they appear on the log. Once the workflow has been set-up, any change in conditions is automatically translated in an update of the correlations; this would not be possible with laboratory experiments.
We show that the actual log response is faithfully predicted by our modelling for two wells in a N-Sea chalk reservoir.
This study was presented at the SPWLA symposium in Cartagena, 2012, and received a Best Paper award. Also published in Petrophysics Vol.54, No.2, April 2013.
Heterogeneous Carbonate Reservoirs: Ensuring Consistency of Subsurface Models by Maximizing the Use of Saturation Height Models and Dynamic Data
Iulian Hulea, Shell
Attempts to characterize carbonate reservoirs follow various rock-typing methods that focus on Special Core Analysis (SCAL) output where core-derived permeability and capillary pressures play a central role. Given the late stage in a project where these results typically become available, integration with dynamic measurements such as wireline formation testing and well testing data is often overlooked. Mobilities derived from formation testers can be compared to permeabilities obtained from various averaging methods. Where no core permeabilities are available, a permeability curve may be derived based on the capillary pressure data that is already part of the model.
Laboratory Test Methods for Determining Capillary Pressure Data
Albert Hebing – Laboratory Manager – PanTerra Geoconsultants
Core capillary pressure data provide fundamental input to reservoir models and saturation-height functions that in turn are necessary to calculate STOIIP and initialise reservoir simulation models. As SCAL data experiments are seen as the “ground truth” in formation evaluation, it is therefore important that the appropriate test method is selected, and correct data interpretation is done.
This DPS presentation is to give an overview of the various analytical techniques that are employed in the industry to obtain Pc lab data, and the advantages and limitations of each individual method.
“The evolution of life-cycle petrophysical evaluation and data acquisition techniques in NAM”
Oscar Kelder – NAM
Oscar will present a talk on how evaluation and data acquisition techniques in life-cycle petrophysics in NAM has evolved over the years, its current challenges and its direction in the future.
“Amstel field – from first oil discovery to first oil production”
Danijela Krizanic – Engie
Located 12km NW of Scheveningen beach, the field holds a title of the first oil discovery in the Dutch offshore. Although it has been discovered in 1962; it has not been put into production until early 2014.
The presentation will cover the progress of the field development since its discovery with focus on reservoir characterization aspect of the project.
– Holds MSc in Petroleum Geology from University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering. She worked for INA Oil Company and Baker Hughes before joining Engie in 2009. Currently she works as asset Petrophysicist for Dutch offshore oil and gas fields.