Reservoir characterization is only as good as the information used to create it—so your data needs to be accurate and up-to-date. To ensure your data measures up, you need to continually reconfirm your geologic models and determine changes in zonal characteristics.
Geological imaging is a key component in your formation data set, revealing the structure and architecture of your reservoir through high-resolution logs. Applications include understanding complex structures, identifying faults and fractures, determining dip angles, and evaluating secondary porosity. With high-quality geological information, you can better characterize your reservoir and more accurately book your reserves.
Acquiring Microresistivity Borehole Images in Deviated and Horizontal Wells Using Shuttle-Deployed Memory Tools
Robert William Christie and Peter A.S. Elkington, Weatherford; Ian McIlreath and Thanos Natros, EnCana Corporation
Borehole images have broad applications in geological, petrophysical, and geomechanical studies. The advent of the small-diameter memory resistivity microimaging tool improves operational efficiency in a broad range of well types. In spite of the tool's small size and weight, its design provides coverage and image quality that matches or exceeds that of previous generation imaging tools. It is deployed with or without a wireline and is not constrained by wireline data transmission rates because data are recorded to internal memory. Deploying the tool inside the drillpipe on the well shuttle facilitates access into highly deviated wells and past bad hole conditions without compromising borehole coverage. Finding fractures in deep and tight rocks has become a high priority among explorationists around the world. Recent discoveries have shown that fractures can play an important role in the productivity of low-permeability plays, such as coalbed methane or shale gas. The only logging technology with the resolution to detect and identify these small features within the reservoirs is borehole imaging, where 2-mm details can be visualized. Deviated wells in the Western Canadian Sedimentary Basin were logged using memory borehole imaging tools. The tools were housed inside a special drill collar while running in the hole, allowing rotation and circulation, and were deployed using a messenger system and pressure pulses. The tools recorded microresistivity data to memory as the drillpipe was then tripped to surface. In all wells, data was recovered, processed, and interpreted using software specially developed for this new memory-based technology. The resulting images were the equal of electrical borehole images obtained using conventional wireline deployment. Using the memory imaging tool housed in the special drill collars protects the tools while tripping into the well. Since there is no wireline and no wet latches, the shuttle system is more robust than conventional tool-pusher systems. This reduces risk and logging operation time while simultaneously delivering high-resolution borehole images that allow these fractured reservoirs to be properly evaluated.
A Memory Cross Dipole Sonic Logging Tool and its Conveyance in Challenging Wells
Peter John Williams, Peter A.S. Elkington, Terry Mayor, and David Eccles, Weatherford;| Daniel Lester Long, Precision Energy Services
Sonic logs provide key data for seismic velocity models and have application in a broad range of drilling, completions, and production challenges related to rock deformation. A new small-diameter wireline-style sonic logging tool with memory capability reduces acquisition risk and extends the application of data into wells that are technically or commercially challenging for conventionally sized tools (such as slim and/or high-dogleg-severity wells and wells where logging out of drillpipe may be the only cost-effective evaluation option). Innovations in the design of the flexural wave transmitter, acoustic attenuator, and receiver assemblies allow compressional and shear velocities and shear anisotropy to be determined from a uniquely small package that is not constrained by wireline data transmission rates (and can therefore be combined with the microresistivity imager and other high-data-density tools without compromising logging speed). Performance is reviewed from operations around the world. Logs from shallow and deep reservoirs, including both conventional and unconventional reservoirs, demonstrate the robustness of the data over a broad range of common environments. The ability to accurately characterize slow formations (including from enlarged borehole intervals) is demonstrated, and minimum horizontal stress orientations inferred from the tool are shown to be consistent with independent analysis from image log data.
Unconventional Reservoir Formation Evaluation Challenges Addressed With Deployment-Optimized Open Hole Logging Solutions
A. Hameed, M. Bacciarelli, and P.J. Williams, Weatherford
It is estimated that only one-third of the remaining worldwide oil and gas reserves are conventional, and the other remaining reserves are in unconventional reservoirs whose evaluation requires appropriate measurements delivered in a cost-effective way. In the case of shales and other tight reservoirs, the defining characteristics are low matrix porosity and low or ultralow permeability, which requires artificial stimulation to encourage production. The optimum stimulation strategy for a particular reservoir is strongly dependent on the distribution of organic material, on the mechanical and geometrical properties of the rock, and on the associated stress field. It is essential to quantify these to an appropriate level of certainty, and well logs are the primary source of such data. Until recently, the options for acquiring appropriate logs in high-angle and horizontal wells have been constrained by either the limited available sensors or the tool conveyance methods. However, the introduction of memory-capable, small-diameter, specialized tools and multiple innovative conveyance options has changed the cost-benefit balance for the better. This paper reviews the current status of openhole log measurements with full spectrum conveyance options and how they impact the evaluation of these challenging reservoirs.
Leveraging Slim Hole Logging Tools in the Economic Development of the Ghawar Fields
I. Ariwodo, A.R. Al-Belowi, and R.H. Bin Nasser, Saudi Aramco; R.S. Kuchinski and I. Zainaddin, Weatherford
Traditionally, brown field developments have often required the plugback and sidetrack of existing drain holes to target any nearby opportunities. With advances in drilling technology, there is a general preference to drill small-diameter wells because of the comparative cost advantage. In the recent times, this preference has led some wireline service companies to start to offer openhole formation evaluation services with slim tools with diameters in the 2-in. to 2½-in. range. At present, most traditional petrophysical measurements can be acquired using slim tools. In addition, several "specialized” measurements, such as cross dipole sonic, formation pressure testing, and resistivity imaging, can also be acquired. The use of battery and memory technologies has allowed deployment of these tools using a broader range of conveyance techniques for reduced risk in the entry of slim wells. The provision of slimhole logging services has created an opportunity to leverage these tools for the economic development of brown fields. Therefore, short horizontal sidetracks and well re-entries to test deeper horizons can be drilled and logged successfully. Saudi Aramco has leveraged these tools in its continued development of the giant Ghawar field. Some of the development projects are listed below: Some horizontal sidetracks with 3-in. hole sizes have been drilled under higher doglegs than was previously possible and logged successfully. It is now possible to run well completions in newly drilled wells that have a well control problem. A provision is made to subsequently log these wells with slim wireline logging tools. It is now possible to run a complete suite of wireline logs across some old wells that were previously completed without a full formation evaluation logging suite. Slimhole formation resistivity imaging services are now being provided to aid in identification of borehole breakout and fracture features that might affect the well productivity. Slimhole formation pressure testing has been acquired in slim wells to generate a pressure gradient, determine oil mobility, and define oil-water contacts.
The Role of Resistivity Image Logs in Deep Natural Gas Reservoirs
Robert Kuchinski and Paul Kalathingal, Weatherford
Occurrences of deep gas are commonly found in clastic reservoir rocks. The great depths of these reservoir rocks often result in rocks with low porosity and poor permeability. In order for these reservoirs to be productive, natural fracture systems or induced fractures from stimulation processes are required to allow gas to flow to the wellbore. In order to assess the potential of these reservoirs, explorationists around the world depend on data acquired from resistivity imaging tools to visualize the fractures. This paper will discuss fracture analysis using resistivity image data that provides better reservoir characterization of a fractured reservoir than the normal openhole logs. Image data has higher resolution than basic openhole data and allows for fracture visualization down to 2 mm. Petrophysical analysis using basic openhole data will average out the fine details of the fracture and its effects on porosity and permeability. Image-based petrophysics, known as "Image petrophysics,” allows for the conversion of high-resolution image data to high-resolution petrophysical properties, which provides greater understanding of the impact of the fractures on reservoir characterization. The use of Image data calibrated with either core data or basic openhole data allows for the derivation of high-resolution porosity distribution. Permeability derivation can also be achieved using image data calibrated with core data. This process can also be extrapolated to wells that are uncored. This paper will also discuss the challenges of acquiring image data from these deep environments by using memory based image tools that can be conveyed using a broad range of conveyance techniques.
Our portfolio of formation imaging technologies and services help you define the geology of nearly any field.
Weatherford geological services are available for a wide range of wellbore environments, and the data-acquisition method can be customized for your operation. From large-diameter holes to slim horizontal wells, we can reliably and accurately log wells with diverse geometries, temperatures, and mud types.
The Compact™ microimager (CMI) tool addresses the two primary challenges operators face when logging a well: conveyance and wellbore coverage.
The versatile conveyance options and dynamic range measurement electronics in the CMI enable it to produce detailed, fullbore images even in challenging well profiles. The CMI is the only imaging tool in the industry capable of deployment through drillpipe into open holes to acquire geological details with or without wireline.
The high-definition images delivered by our Compact tools are complemented by our unique image reconstruction and visualization services.
After logging your well, we enhance the data using our patented Reveal 360™ image-processing technology, which reconstructs gaps in data with appropriate values based on the structural and textural information in the measured parts of the image.
Collaboration between Weatherford wireline services and operators has yielded economic benefits for our clients.
We worked with one of our clients to develop a custom imaging solution for their horizontal development programs. Within 180 days of incorporating the CMI tool into their completions strategy, the operator saw initial oil production rates increase nearly 40%. This success led the operator to adopt Compact imaging technology more broadly, which resulted in production gains from all of their horizontal development programs.