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Abstract Over the last decades horizontal drilling has been performed on the StatoilHydro operated Troll field. During this time the total distance of horizontal wells within the reservoir has exceeded 1.600.000 feet, and Logging While Drilling (LWD) has been utilized to log gamma ray, resistivity, density and neutron porosity. This tremendous amount of horizontal resistivity data acquired over time gives us an opportunity to assess how log response interpretation changes with time. When the first horizontal wells were drilled the field was in its virgin state and horizontal log interpretation was in its infancy. Over time the understanding of the horizontal log responses has improved. Tremendous changes in drilling technology and better knowledge of horizontal log responses and the impact on wellbore placement have led to an exceptional good production from the field. Over the last decade the Troll field has entered a more mature state, and log interpretation has become more challenging as the log responses are clearly affected by production. A second complicating factor is the variation in sand quality within the reservoir, from extremely high porosity and permeability to medium to high porosity and permeability. The third complicating factor is the presence of calcite cemented sandstone nodules which gives a very high resistivity reading in the near zero porosity rock. This paper illustrates the steps necessitated in the horizontal log interpretation over time when the field is changing from virgin to mature, and discussing the factors having the greatest influence on the horizontal resistivity log responses. To improve our understanding of horizontal resistivity log responses, we examine facies across the field and the effects of fluid movements. Recently, azimuthal propagation resistivity has been utilized on the Troll field. These measurements add a new dimension to horizontal resistivity log interpretation. Introduction Located offshore on the Norwegian continental shelf, the Troll field is one of the world's largest gas fields, with a gas leg of up to 200 meters and only a thin oil leg. Nevertheless, Troll has over the last decades become one of largest oil producers on the Norwegian sector. Figure 1 shows the net oil and gas production from the Troll field. The Troll field consists of two main structures, the Troll East and Troll West, both having a thin oil column below the gas cap, thus far only the Troll West structure with an oil leg of 11–26 m, has been found to be commercially viable. Oil production from the Troll field is based on a gas-cap drive mechanism. A strong belief in the feasibility of developing the thin oil leg on Troll West, combined with enabling horizontal drilling technology, lead to the first successful horizontal production well being drilled on Troll West in 1989. In addition to the new horizontal drilling technology, state of the art LWD formation evaluation logging tools were utilized right from the start of drilling these horizontal wells. 1.600.000 feet of horizontal drilling and logging has been performed since the first horizontal well was drilled.
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Sognefjord Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Heather Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Fensfjord Formation (0.99)
- (15 more...)
The nature of fluid flow in a formation intersecting a cylindrical borehole is studied by solving the radial diffusion equation with a sinusoidal pressure condition in the borehole. The penetration distances of the pressure and velocity fields into the formation are computed. The effects of varying permeability, viscosity, frequency, borehole radii and porosity are studied. The results show that the penetration distance can vary from the order of millimeters to the order of meters depending on the specific combination of these parameters. The results of this study can be used as a basis for interpreting the permeabilities estimated from Full Waveform Acoustic Logs and Vertical Seismic Profiling and to design experiments and tools with frequency characteristics appropriate for desired depths of investigation.
- South America (1.00)
- North America > United States > Wyoming (1.00)
- North America > United States > Oklahoma (1.00)
- (17 more...)
- Research Report > New Finding (1.00)
- Overview > Innovation (1.00)
- Research Report > Experimental Study (0.65)
- Phanerozoic > Paleozoic (1.00)
- Phanerozoic > Mesozoic (0.67)
- Phanerozoic > Cenozoic (0.67)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Sedimentary Geology > Depositional Environment > Marine Environment (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (1.00)
- (7 more...)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.45)
- South America > Venezuela > Anzoátegui > Eastern Venezuela Basin > Maturin Basin > Hamaca Area (0.99)
- South America > Argentina > Jujuy > Salta Basin > Caimancito Field (0.99)
- South America > Argentina > Jujuy > Noroeste Basin > Caimancito Field (0.99)
- (103 more...)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Near-well and vertical seismic profiles (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
ABSTRACT A particularly troublesome type of noise in log data is caused by large, sharp and usually isolated changes in the measured numerical values of the data. An example of this type of impulse or spike noise is cycle skipping in sonic log data. Problems are encountered in the interpretation and processing of data contaminated by this type of disturbance. In particular, mathematical algorithms designed to increase the vertical resolution of the measurements can be severely degraded over large depth intervals whenever even a few impulse errors are present in the data. The poor performance of these inverse filters in the presence of impulse noise has limited their use on a routine basis. A new algorithm has been designed to detect the presence of these noise spikes, to locate the exact position in the data where the spike occurs, and to automatically correct the erroneous data. The algorithm utilizes the innovations properties of a previously presented deconvolution algorithm to accomplish the error detection and correction. After the data are corrected, the algorithm is used to increase the vertical resolution of the data. Correction of cycle skipping errors in sonic data is one application, but the algorithm is general and can be applied to any log data for which the response function of the tool used to acquire the data is accurately known. Synthetic sonic log data are used to explain the structure and workings of the algorithm. Examples are presented to show the application of the algorithm to real sonic log data containing cycle skips as well as a more subtle, and in some cases, equally troublesome type of impulse noise due to uneven tool movement or tool jitter. A skilled interpreter can visually detect cycle skips, but noise due to tool jitter can generally be detected only by an algorithm of the type described here.
ABSTRACT A new MWD gamma ray tool using high density material to focus detection of radioactivity in both the upper and lower sections of the borehole has been developed. In addition to formation correlation capability, the focusing characteristic of the gamma detector allows detection of approaching bed boundaries in near horizontal wells while drilling, allowing controlled drilling between bed boundaries. The focusing characteristic of the gamma detector can possibly be used to provide detection of vertical fractures in horizontal wells when the fractures contain radioactive material. This paper will describe the design and successful field application of the MWD directional-focused gamma ray tool. Log examples are presented showing response to approaching bed boundaries, vertical radioactive events and elliptical boreholes in a horizontal well.
What Next After a Decade with Significant Advances in the Application of Deep Directional Measurements?
Antonsen, Frank (Equinor ASA) | Danielsen, Berit Ensted (Equinor ASA) | Jensen, Kåre Røsvik (Equinor ASA) | Prymak-Moyle, Marta (Equinor ASA) | Lotsberg, Jon Kåre (Equinor ASA) | De Oliveira, Maria Emilia Teixeira (Equinor ASA) | Constable, Monica Vik (Equinor ASA)
Abstract Equinor has played an important role the last decade in testing and development of ultra-deep azimuthal resistivity (UDAR) measurements both for Look-Ahead and Look-Around applications. Today, more than 70% of Equinor high angle or horizontal wells are drilled with UDAR-technology. In this paper, the authors will review the use of UDAR in Equinor the last decade and highlight both successful use and real-time challenges related to interpretation of the inversion results. UDAR-technology and inversion algorithms have been very powerful for reservoir mapping to geosteer or geostop according to plan. However, we forget far too often the fact that we need a good understanding of the reservoir to interpret and evaluate the uncertainty in the inversion result. The number one mistake in a real-time setting is to interpret a resistivity contrast as a specific layer in the reservoir (for instance top reservoir) and hold on to that same interpretation even if we drill away from that contrast and may cross multiple layers as distance to the observed contrast increase. Other challenging real-time UDAR-exercises relate to uncertainties in the prediction of resistivity inside the reservoir and reservoir thickness from inversion results when still drilling above the reservoir. A third mistake often seen real-time is detailed interpretation of 1D-inversion results, even when other indicators are pointing towards 2D/3D complexities in the reservoir. Equinor and other operators have pushed for more and more advanced inversion solutions leading to 3D mapping capabilities for more complex reservoirs. The UDAR advances the last few years are important for Equinor's planned roadmap ahead. However, 1D-3D inversion results can result in wrong decisions if the uncertainty in the inversion result is not managed correctly. We see a need to investigate how to best exploit UDAR-technology and inversion results within its limits, but also ensure assumptions are not extended beyond an acceptable uncertainty level. Better handling of uncertainties in geosteering operations will become increasingly important for the well economy with smaller targets, complex geological settings, and varying sweep efficiencies. How can we best handle the uncertainty in inversion results in real-time operations to avoid wrong decisions that can potentially destroy well economy? This is an important question which will be addressed and should be handled in the future if UDAR-technology is to continue having an important role in many of the wells to be drilled the next decades.
- Europe > Norway (0.94)
- Asia (0.93)
- North America > United States (0.67)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.87)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 050 > Block 34/10 > Gullfaks Field > Statfjord Group (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 050 > Block 34/10 > Gullfaks Field > Lunde Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 050 > Block 34/10 > Gullfaks Field > Lista Formation (0.99)
- (2 more...)
- Well Drilling > Drilling Measurement, Data Acquisition and Automation > Logging while drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- (5 more...)