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Abstract The well drainage pressure and radius are key parameters of real-time well and reservoir performance optimization, well test design and new wells' location identification. Currently, the primary method of estimating the well drainage radius is buildup tests and their subsequent well test analysis. Such buildup tests are conducted using wireline-run quartz gauges for an extended well shut-in period resulting in deferred production and risky operations. A calculation method for predicting well/reservoir drainage pressure and radius is proposed based on single-downhole pressure gauge, flowing well parameters and PVT data. The proposed method uses a simple approach and applies established well testing equations on the flowing pressure and rates of a well to estimate its drainage parameters. This method of estimation is therefore not only desirable, but also necessary to eliminate shutting-in producing wells for extended periods; in addition to avoiding the cost and risk associated with the wireline operations. The results of this calculation method has been confirmed against measured downhole, shut-in pressure using wireline run gauges as well as dual gauge completed wells in addition to estimated well parameters from buildup tests. This paper covers the procedure of the real-time estimation of the well/reservoir drainage pressure and radius in addition to an error estimation method between the measured and calculated parameters. Furthermore, the paper shows the value, applicability and validity of this technique through multiple examples.
This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 146732, ’Geosteering With Sonic in Conventional and Unconventional Reservoirs,’ by Jason Pitcher, SPE, Jennifer Market, and David Hinz, Halliburton, prepared for the 2011 SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November. The paper has not been peer reviewed. Azimuthal variations with sonic logs have been observed in wireline and logging-while-drilling (LWD) data. Basic reactive-geosteering methods have been used, including drilling until a real-time sonic log detected a change in formation velocity then altering the wellbore trajectory. Taking sonic geosteering a step further has been proposed by providing real-time azimuthal images that show the velocities as they vary around the wellbore. These images can be transmitted at shallow and deep depths of investigation (DOIs) to determine how close an approaching boundary might be. Introduction LWD sonic tools have been used for simple geosteering since their introduction in the 1990s. The measurements typically were limited to the compressional-wave arrivals and (if available) refracted-shear-wave velocities. The use of real-time information was limited to simple correlation or direct-interpretation techniques. The practical use of these measurements was limited by the complexity of the measurement in terms of environmental conditions. These tools have found new application and use in recent work in shale-reservoir systems, including the Haynesville, Eagle Ford, Woodford, and Marcellus. In addition to using the compressional- and shear-wave data, these measurements are processed to provide dynamic data for Young’s modulus and Poisson’s ratio. The tools then are used to produce a real-time brittleness index that can be used to land and geosteer within the optimal production zone. Measurement Considerations DOI/Depth of Detection. The sonic-tool DOI depends on the source frequency, formation resonant frequency, source/receiver spacing, and the configuration (i.e., monopole, dipole, or quadrupole) of the source. A general rule of thumb is to estimate the DOI as approximately one wavelength. Thus, for a given formation, a high-frequency source (10 kHz) would yield half the DOI of a low-frequency source at 5 kHz. Or, use of the same 10-kHz source in a 100sec/ft-velocity formation vs. a 50-sec/ft-velocity formation, the 50sec/ft-velocity formation would have a deeper DOI. This effect is complicated by each formation having a natural resonant-frequency range. In general, fast formations favor high frequencies and slow formations favor low frequencies. Annulus size also can affect the resonant frequency: A small annulus shifts the resonant-frequency range higher than a large annulus. Though the rule of thumb is a reasonable starting estimate, several factors can increase or decrease the DOI. Fig. 1 shows the effects of frequency and slowness on DOI.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.37)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.35)
Abstract Accurate placement of the borehole within the reservoir and identification of features impacting producibility are key elements for success. Experience to date, shows that the drilling environment offers a good platform for high definition electrical borehole imaging. At the time of drilling, invasion and borehole wall rugosity are often minimal and electrical images generated by sensors that rotate with the drill string provide a full coverage of the borehole. It also provides an opportunity for real-time geological analysis while drilling and the decision making that is unavailable with wireline. Detailed analysis of images reveal discrete sedimentological and textural features aiding facies recognition in carbonate reservoirs. These facies can be up-scaled to facies associations and eventually used for depositional environment interpretation. This leads to wider prospect delineation and confirmation of the local geological model. The study also demonstrates the strength of early geological information in high-resolution for reducing geological uncertainty at an early development drilling program. We show case studies from several carbonate reservoirs in which high resolution electrical images have been acquired in conjunction with reservoir navigation (well placement). From post well analysis, we can define the key criteria that help in recognition of reservoir position; correlatable sedimentary surfaces and image facies/patterns. We test the distribution of facies and sedimentological features that can be recognised in horizontal boreholes by comparison to vertical offset wells, in addition to automated facies recognition from image log responses. The development of a Sedimentary or carbonate facies steering technique using high-resolution images with a predictive and real-time interface will reduce uncertainties related to and better aid geosteering within the desired "sweet-spot" of a variety of clastic and carbonate reservoirs.
- Africa (0.68)
- Asia > Middle East (0.28)
- Geology > Sedimentary Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.85)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Borehole imaging and wellbore seismic (1.00)
- (2 more...)
Abstract In the quest to increase reservoir contact, horizontal drilling and multi-stage hydraulic fracturing is the common theme in the stimulation of productive shale reservoirs. Twenty to thirty stage fracs are not uncommon in some of these reservoirs. Cost, and sometimes safety considerations, can lead operators to make do with minimal information in the laterals. The selection of frac intervals is often guided by measurements in the pilot hole and stages are placed more or less evenly along the lateral. Field examples presented here highlight the fact that comprehensive LWD or openhole wireline data, acquired with the special deployment techniques in the lateral, clearly demarcate the good zones (sweet spots) from intervals with inferior reservoir characteristics. LWD Spectral GR has proved its worth in this regard and an innovative acoustic LWD measurement has provided valuable data in the laterals that has aided stimulation design. An original approach involving real time monitoring of hydrocarbon (C1 – C8, benzene, toluene) and non-hydrocarbon gases (CO2, N2) dissolved in the drilling fluid in the mud stream has proven successful in independently identifying sweet spots in the laterals. On the other hand, near real time measurements of XRF, XRD and pyrolisis measurements on drill cuttings at the wellsite have clearly established their worth in identifying zones suitable for stimulation. Field examples presented here demonstrate how these techniques have been successfully used to identify sweet spots and have thus helped enhance the effectiveness of hydraulic fracturing, resulting in improved production from shale reservoirs. Production data are presented to show how productivity is enhanced by concentrating on sweet spots.
- North America > United States > Texas (0.94)
- North America > Canada (0.69)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.69)
- North America > United States > Texas > Haynesville Shale Formation (0.99)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- North America > United States > Louisiana > Haynesville Shale Formation (0.99)
- (8 more...)
Abstract Assurance of wellbore stability (WBS) is of utmost concern and a key challenge in drilling an inclined well in ultra deep water of the East Coast of India. The WBS analysis requires accurate modeling of earth stresses and rock mechanical properties. These processes are primarily based on sonic logs (compressional and shear slowness), bulk density and lithological distribution. To understand and address drilling complications in the study area, post-drill (offset well analysis) and real-time drilling geomechanics is carried out in this well. 1D mechanical earth model (MEM) and WBS model is constructed for offset wells, which is calibrated with caliper log, pressure test and leak-off data sets. WBS analysis suggested drilling with lower mud weight in the zones of shear failure and pack-off. Disparity in resistivity values is also observed when wireline logs and Logging-While-Drilling (LWD) logs are analyzed. This might be due to mud invasion or fluid-shale interaction in the open hole, as it is resolved by changing mud system from water based mud (WBM) to synthetic oil base mud (SOBM). The post-drill analysis of offsets wells established parameters for the upcoming inclined well. The planned well is the first inclined well (horizontal drift more than ∼2000m) in ultra deepwater of the East Coast of India to avoid the drilling risks; real-time drilling geomechanics is first time put into operation. Required sonic and density data is received in reasonable time intervals to perform real-time analysis. Timely updates on rock mechanical properties are provided to client, which helped in optimizing drilling parameters. As a result, first inclined well in ultra deep water in the East Coast of India was drilled successfully.
- Well Drilling > Wellbore Design > Wellbore integrity (1.00)
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Drilling Fluids and Materials (1.00)
- (2 more...)
Reducing Uncertainties in Casing Depth and Formation Evaluation Using Look-Ahead Logging While Drilling Technology
Deri, C. Peter (Schlumberger) | Peternell, Ana (Schlumberger) | Hebert, John (Schlumberger) | Fisher, James L. (Stone Energy Corporation) | Gibbs, Rudy B. (Stone Energy Corporation) | Cornell, Robert (Schlumberger) | Moreno, Javier (Schlumberger)
Abstract Logging while drilling (LWD) technology has been used successfully to overcome the drilling challenges when exploring a caprock hostile environment in the Main Pass area of the Louisiana Gulf Coast. Because of the geological setting, special steps needed to be taken to mitigate the obstacles and uncertainties while drilling. Successful acquisition and application of selected measurements led to achieving the drilling and formation evaluation objectives. To drill the optimal wellbore, seismic-while-drilling technology was employed to optimize casing depths and minimize drilling risks such as mud losses and potential H2S. Additional techniques were used to help make the decision to set casing and maintain a viable wellbore for logging and completing the well. For the second challenge, providing formation evaluation without compromising drilling safety and data quality, additional LWD services were applied. A resistivity-at-the-bit laterolog imager and a multifunction formation evaluation platform were employed to satisfy both the drilling demands and the formation evaluation needs. Having drilling mechanics and formation evaluation measurements available provided not only advanced measurements closer to the bit, giving a better chance of reducing invasion effects, but also impacted the drilling time through shorter rathole section. In addition, the laterolog resistivity imaging provided dips and texture information to map the structure and identify different geological features. Using these technologies, 100 ft were drilled into the caprock with enough information to evaluate the economical value of the prospect reservoir. The combination of these technologies and the ability to interpret the data streamed while drilling allowed the operator to successfully set casing at the top of the limestone caprock. In the end, the drilling risks and uncertainties experienced in the past were totally eliminated by the proper use of LWD technology.
- North America > United States > Louisiana (0.24)
- North America > United States > Gulf of Mexico > Central GOM (0.24)
- Geology > Mineral (0.95)
- Geology > Petroleum Play Type (0.84)
- Geology > Rock Type > Sedimentary Rock (0.49)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
Abstract Carbonate formations are highly heterogeneous with variations from grainstones to mudstones. Digenesis leads to changes of the rock's original nature, like dolomitization, vugs, layering and fracturing. These variations have effects on rock quality in terms of porosity and permeability. Similarly, clastics, including shaly sands, can be quite challenging in terms of accurate formation evaluation. Although extensive logs are run for the petrophysical evaluations in these formations, the use of advanced wireline formation testers (WFTs) greatly aids reservoir description. Standard formation evaluation tools and techniques sometimes result in low level of confidence in identifying and quantifying the presence of hydrocarbon in certain reservoirs. The application of modern wireline formation testers has become a useful tool in minimizing uncertainties in situations where we have low confidence in log evaluation. Some borehole conditions and reservoir architectures, like fractures, vugs, and low mobility and mud losses could also pose some challenges while performing formation testing. In this paper, several examples and case histories of the application of advanced wireline formation testers across varieties of rocks with fractures, vugs and different borehole conditions are presented. Results indicate that reservoir heterogeneities can be described and quantified more accurately with the integration of dynamic data to aid reservoir characterization. This paper also demonstrates how to handle the challenges of detecting the early traces of hydrocarbon arrival for real time decisions during pressure testing and sampling.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.54)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.54)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Pressure transient analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Formation test analysis (e.g., wireline, LWD) (1.00)
Abstract Data acquisition in extreme environments of high pressure and/or high temperature (HPHT) with pressures up to 30,000 psi and temperatures up to 500°F requires not only specialist technology capable of surviving these conditions, but also many months of preparation and planning to ensure a successful operation. The aim of this publication is to provide an overview of what is involved in the planning, preparation and execution of an extreme HPHT wireline data acquisition, from the customer setting the information objectives through to data delivery. This includes developing an agreed quality plan between the data provider and the customer covering testing and deployment of the latest extreme HPHT logging equipment. All aspects must be considered to minimize risks including detailed tailoring of the logging programmes to manage time in hole, ensure accurate depth control and by employing a deployment risk management process, to ensure that what goes in the hole comes out again. The implementation of these procedures is illustrated with a case history of a series of HPHT exploration wells drilled in the Central Graben of the North Sea (the "HPHT Heartland" of the North Sea). Bottom hole conditions were predicted to approach 400°F and 15,000 psi. These extreme conditions negated the use of conventional wireline tools and so, from initial early planning discussions between client and service provider, new detailed programmes were designed and implemented as a specific "Quality Plan" to use the advanced HPHT wireline logging tools.
- Europe > United Kingdom > North Sea > Central North Sea (0.24)
- Europe > Norway > North Sea > Central North Sea (0.24)
New Generation Magnetic Resonance While Drilling
Heaton, Nicholas (Schlumberger) | Jain, Vikas (Schlumberger) | Boling, Brian (Schlumberger) | Oliver, David (Schlumberger) | Degrange, Jean-Marie (Schlumberger) | Ferraris, Paolo (Schlumberger) | Hupp, Douglas (Schlumberger) | Prabawa, Hendrayadi (Schlumberger) | Torres Ribeiro, Mauro (OGX) | Vervest, Edwin (BP) | Stockden, Ian (BP)
Abstract In this paper, a new series of Logging-while-drilling (LWD) nuclear magnetic resonance (NMR) tools is introduced. The tools incorporate a magnet arrangement which provides a low field gradient minimizing adverse lateral motion effects. T2 distributions are measured while drilling or sliding in a range of hole sizes, including large holes previously inaccessible to LWD NMR measurements. Benefits and trade-offs of key tool design features are presented. Emphasis is placed on measurement quality, operational simplicity and log quality control in real time and memory mode through example logs from operator wells. Real-time T2 distributions provided by the new generation LWD NMR tool enable a full range of NMR answers, including lithology-independent total porosity, bound fluid volume and permeability. Real-time log quality controls monitor tool noise, antenna sensitivity, tuning quality and lateral motion. Acquisition sequences are optimized for porosity precision and accuracy in different environments. Drilling data have been acquired in several operator wells and a test well covering diverse ranges of formations and logging conditions. Environmental factors affecting porosity precision and T2 quality are discussed with reference to log quality indicators and comparison with wireline NMR logs is made where available. In general, the LWD tools deliver NMR answers comparable to the analogous wireline logs in terms of precision, accuracy and vertical resolution. With increased industry focus on LWD services and heightened sensitivity to downhole chemical sources, the need for reliable LWD NMR measurements continues to grow. In addition to a sourceless porosity measurement, NMR provides unique quantitative information on the disposition of producible fluids, which is not available from other logs. Real-time producibility information can be used to optimize formation pressure measurements and sampling as well as for timely completions and well placement decisions. The new generation LWD NMR tools introduced here addresses this need.
Improving Well Placement and Reservoir Characterization with Deep Directional Resistivity Measurements
Constable, Monica V. (Statoil) | Antonsen, Frank (Statoil) | Olsen, Per Atle (Statoil) | Myhr, Gjøril M. (Statoil) | Nygård, Atle (Statoil) | Krogh, Morten (Statoil) | Spotkaeff, Matthew (Schlumberger) | Mirto, Ettore (Schlumberger) | Dupuis, Christophe (Schlumberger) | Viandante, Mauro (Schlumberger)
Abstract The last decade has shown a significant development in resistivity measurement technology providing directional resistivity at a larger scale than conventional logging tools. The latest development can identify resistivity contrasts ten's of meters around the wellbore. Statoil has tested deep look-around resistivity on a range of fields during the last 2 years and recorded data in more than 10 wells on the Norwegian Continental Shelf. The look-around images provides information at a scale that bridges the gap between conventional logging and seismic and adds important new pieces to the reservoir characterization puzzle. In good reservoir conditions, resistivity contrast up to 30 m away from the well-bore has been observed. This study will focus on results from the Visund and Åsgard fields, and will demonstrate how the device was used in a range of different applications in the geosteering operation: Detection of the reservoir boundary up to 20m TVD away. Detection of oil bearing reservoir from within underlying shale, through a water zone. Detection of Gas-Oil Contact (GOC). Detection of Oil-Water Contact (OWC) up to 20m TVD away. Detect faulting of the reservoir. These examples will highlight why deep look-around resistivity is a step change related to the possibility for doing pro-active well placement of highly deviated wellbores as well as for gaining a larger reservoir understanding. The imaged variation in resistivity contrasts can be related to geologic zonation and fluid content on the reservoir scale, which opens up a much better cross-disciplinary communication between geophysicists, geologists, petrophysicists and reservoir engineers. Finally, the deep resistivity images contribute in optimization of completion solutions when incorporating information on the reservoir scale.
- Europe > Norway > Norwegian Sea (0.89)
- Europe > Norway > North Sea > Northern North Sea (0.47)
- Geology > Geological Subdiscipline > Stratigraphy (0.69)
- Geology > Structural Geology > Fault (0.68)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.35)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.46)
- Europe > Norway > Norwegian Sea > Halten Terrace > PL 479 > Block 6506/12 > Åsgard Field > Smørbukk Sør Field > Åre Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > PL 479 > Block 6506/12 > Åsgard Field > Smørbukk Sør Field > Tofte Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > PL 479 > Block 6506/12 > Åsgard Field > Smørbukk Sør Field > Tilje Formation (0.99)
- (93 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 > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)