Complexity of well design has increased significantly with better understanding of reservoirs. As a result, the drilling industry has shifted from vertical wells to more deviated, S-shaped, horizontal, and multilateral wells. Complex wellbore geometries, such as tortuosity, hole stability, and low-pressure zones, make conventional wireline conveyance problematic and often impossible.
Wireline conveyance includes transporting logging tools from the surface to the desired depth, acquiring logs, and retrieving the tools and data in a safe and efficient manner.
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.
A Pressure Activated Deployment System for Openhole Memory Logging Tools and its Application in Directional Wells
M.C. Spencer, S.C. Ash, and P.A.S. Elkington, Reeves Oilfield Services
Openhole memory logging was introduced in 1999 as a more efficient alternative to pipe conveyed wireline logging. It was developed subsequently into a shuttle system that conveys logging tools inside drillpipe and that provides formation evaluation logs after drilling to supplement basic real-time logging-while-drilling (LWD) data. The original shuttle design used a dart pumped from surface to move the logging string into open hole after the assembly reached TD. In a new development, the dart has been eliminated together with the associated pumping time. In its place is an electro-mechanical pressure-activated release mechanism capable of simple two-way communication. The method has been used in trials to activate and deploy logging tools downhole and to return status information to surface. It has the potential to be developed further for post-drilling real-time data transmission and is a key component in a repeat formation pressure tester being developed for memory operations.
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.
Deployment Strategies to Reduce Risk in the Acquisition of Formation Evaluation Data
Robert Kuchinski, Weatherford
Effective reservoir management requires sound decision making that is based on formation evaluation data acquired during all stages of the life of the well. Without this data, reservoir understanding is compromised, which can impact long-term well productivity. Given the increasing challenges of acquiring data in today's geometrically complex wells, new methods of data acquisition are constantly being developed and refined. This has led to a new area of oilfield innovation called conveyance. This paper is an analysis of the risks associated with the acquisition of formation evaluation data. These risks are generally classified as follows: 1. Nonproductive time due to the inability of logging tools getting to bottom. (bridging) 2. Nonproductive time due to delays associated with making last-minute arrangements for alternative logging methods when bridging problems become too severe. 3. Lost-in-hole charges associated with permanently sticking logging tools due to challenging hole conditions. 4. Unsound decision making throughout the life of the well, because challenging hole conditions made the acquisition of formation evaluation data impossible. The risks outlined above can also be assessed depending upon the data requirements and the conveyance method employed. A new risk assessment will be presented that discusses the risks associated with acquiring the data that provides insight into the six main formation properties required by the industry to understand reservoirs. Several conveyance techniques that assure the acquisition of data will be discussed along with case histories of some of these applications. This paper will serve as a means to understand and assess the risks associated with the acquisition of formation evaluation data. It will also increase awareness of the techniques that exist for acquiring data and ultimately allow for developing the best strategy to acquire formation evaluation data.
Drillpipe Conveyed Logging Provides Solutions for Pressurized Mud Cap Drilling Operations
Julmar Shaun Sadicon Toralde, and Kevin Fisher, Weatherford; David John Collecott, Precision Energy Services; and John C. Stewart, Weatherford
The variant of managed pressure drilling (MPD) used in oil and gas wells that experience severe to total circulation losses accompanied by the persistent influx of reservoir fluids is called pressurized mud cap drilling (PMCD). In this method, the well is closed in on a rotating control device (RCD), and a light, annular fluid column, or mud cap, is maintained in the annulus. Sacrificial drilling fluid—mostly water—is pumped through the drillpipe and together with the cuttings is swept into the loss zones. No returns reach the surface. Once target depth is reached using the PMCD process, subsequent operations (logging in particular) need to interface with PMCD equipment and methods. However, the continued presence of severe losses and the possibility of kicks make it difficult to use conventional wireline logging methods in wells drilled using PMCD. The requirements and difficulties of logging in PMCD mode most of the time lead to the scrapping of the logging program. This paper presents the answer to the challenge of logging safely, efficiently, and successfully in PMCD mode by using a commercially proven compact drillpipe-conveyed logging system known as the well shuttle, in conjunction with a downhole isolation valve (DIV) and the RCD. It provides the set-up of the proposed system and discusses its capabilities and limitations. The advantages and disadvantages of the system, as well as how it compares to wireline logging methods in PMCD operations, are also discussed.
Mitigating the Risks Associated With the Acquisition of Formation Evaluation Data
Robert S. Kuchinski and Robert J. Stayton, Weatherford
Acquiring formation evaluation data is a critical element in the drilling of any well regardless of the location, well type, or well geometry. Risks associated in acquiring data can be classified as follows: 1. Lost rig time due to the inability of logging tools getting to bottom (bridging). 2. Lost rig time due to delays associated with making last minute arrangements for alternative logging methods when bridging problems become too severe. 3. Lost in hole charges associated with permanently sticking logging tools due to bad hole conditions. 4. Unsound decision making throughout the life of the well because bad hole conditions made the acquisition of formation evaluation data impossible. The risks outlined above increase as wells are drilled at faster rates with higher geometric complexity. Advanced drilling technologies allowing for access to difficult to reach petroleum resources will increase as the industry exploits unconventional resources and increasingly complex reservoirs. Recent advances in formation evaluation technology and conveyance techniques allow for the acquisition of high quality petrophysical measurements regardless of borehole conditions or geometry. Logging systems conveyed in the drill string, or through the drill string, have a 100% chance of getting to bottom on the first attempt. With the logging tools securely attached to the drill pipe, the risk of the logging tools getting stuck is also reduced. The non-traditional conveyance techniques discussed in this paper bring operational optimization to formation evaluation.
An Openhole Memory-Logging System for High-Angle Wells and Bad Hole Conditions
P.A.S. Elkington, M.C. Spencer, and D.L. Spratt, (Reeves Wireline Services)
A mechanism for conveying logging tools inside drillpipe has been developed that reduces the risk and cost of acquiring openhole formation evaluation data in high-angle wells and bad hole conditions. The measurement string is housed inside drillpipe, where it is protected while running in and pumped into open hole close to final depth. Wireline tools are used for data-quality reasons, but the wireline has been eliminated, giving time, access, and well-control advantages relative to wireline pipe-conveyed logging (PCL). It is an alternative to the formation evaluation element of logging while drilling (FE-LWD), where steering decisions do not rely on real-time petrophysical analysis, particularly when the risk to the bottomhole assembly (BHA) is high. The system's ability to acquire data while conditioning the hole contributes to its efficiency and is advantageous in bad hole conditions. A 1.4-km horizontal test loop was constructed to help develop and prove the tool deployment and signaling mechanism. Insights gained during this process resulted in the development of novel payload delivery seals— key components in the system. Formation evaluation data have been acquired in 220 wells; they include horizontal wells for which other logging solutions are unattractive for reasons of accessibility and/or cost. Knowledge gained from the interpretation of these data sets has influenced completions in some wellbores and guided remedial action in others.
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.
Assure™ conveyance is all about mitigating risk in complex wellbores, from losing expensive tools to the greater risk—failing to get any data at all.
Assure conveyance overcomes these issues and provides wireline-quality data, with or without wireline. Weatherford has taken Assure conveyance technology to a higher level of open-hole formation evaluation by taking a fresh look at both sides of the logging equation—the logging tools and their conveyance systems.
Our unique memory-capable Compact™ family of logging tools and services provide a full spectrum of evaluation data for making informed drilling and completion decisions. Compact services offer a robust range of logging options and, when paired with the Assure conveyance options, are designed to be the industry’s most efficient solution for logging-data acquisition.
Weatherford Compact technology offers one of the industry’s most flexible logging platforms in the industry.
Our Compact tools can acquire logs with or without wireline, providing a wide range of conveyance options. The Compact well shuttle allows running bigger OD tools in the garage pipe instead of running them through the drillpipe.
Weatherford is an industry leader in providing conveyance solutions. Besides supplying conventional techniques, our unique memory-capable Compact family of tools and services offer a full spectrum of evaluation data featuring 10 distinct conveyance options.
This unique combination helps guarantee delivery of accurate formation-evaluation answers over the widest range of hole sizes, including the most routine wells to the most challenging circumstances. Case studies in every region show that Weatherford reduces the operating costs and acquires high-quality data in holes deemed impossible-to-log by others.