Numerous integrative approaches can be taken to link subsurface rock-type characterization to related openhole wireline log attributes. In this study, focus and emphasis was geared towards developing rock-typing models that link depositional environments to petrophysical property space trends and variations to then guide subsurface modeling. Multiple technical paths were taken, and tools used to link observed rock types in full-diameter conventional cores and related measured geological attributes to electrofacies and the refined petrofacies characterization. The data integration used a significant volume of core analytical and openhole wireline log suites including a base suite of triple-combo data (gamma ray, neutron, density, and resistivity) and expanding to include resistivity borehole image data. We present how the addition of various subsurface datasets impacts rock-typing efforts and accuracy. A cluster-based, least-mean-squares analytical result is observed and discussed in an unsupervised model application and is compared to a supervised model application. The relative importance of various attributes is discussed and used to recommend a workflow for Permian-focused rock typing that allows the subsurface characterization to be extrapolated to regional (basinwide) and local (single-well) scales. In short, we focus on sharing a workflow to effectively link core description (sedimentologic observations) and raw log analytics to refine and upscale rock property distributions for use in sequence stratigraphic frameworks, regional basin depositional models and multiscale modeling efforts.
Each basin has its own geophysical and geologic challenges that we need to address. These will change due to the geology and depth of burial. This paper will investigate challenges in two distinctly different basins. The Delaware basin in west Texas has a severe near surface problem that degrades the quality of seismic within the basin. We will investigate the use of near surface velocity model building tools to build a better understanding of the near surface geology. The Appalachian basin of southwest Pennsylvania offers a different set of challenges. In this area high values of epsilon have been observed. In this case a robust method to determine the anisotropic parameters are necessary for success. With a robust toolbox and the experience to deploy it correctly you can optimize the rate of return for your assets.
Presentation Date: Thursday, October 18, 2018
Start Time: 8:30:00 AM
Location: 204C (Anaheim Convention Center)
Presentation Type: Oral
This paper focuses on an operational review and lessons learned during the deployment of a novel straddle packer system in a refracturing application. The operation involved the deployment of an industry-first high-rate / high-pressure straddle packer to convey a propped refrac job to a previously producing well in a challenging application. The paper will also include relevant notes on operational time optimization derived from the field implementation as well as pre and post-treatment production information.
The paper describes details on overcoming the challenge of effectively isolating a single group of perforations among multiple producing zones of a wellbore in order to deliver a targeted stimulation treatment. The paper also discusses opportunities for improvement and learnings from this novel deployment. Finally the paper analyzes pressure and temperature data gathered during the treatment to assist in understanding job execution as well as post-treatment production information.
The novel stimulation technology enabled the operator to accurately place a propped refrac treatment at 20 bpm in a 200ft-long interval of previously producing perforations in a single run. The application reduced the operational time on location by 30% and reduced the number of runs required to complete the operation. Comparative production results will be shown as a measure of treatment effectiveness.
The paper contributes a novel insight to the intervention, stimulation, and refracturing industries by describing one of the first successful high-rate re-stimulation jobs using a straddle packer with open perforations above and below in a single trip. This insight is relevant as it highlights a cost-effective alternative for reviving existing wells at a fraction of the cost of a new drill, without the need to deploy numerous tools and fluids in multiple trips to achieve the zonal isolation as typically required in a re-stimulation treatment.
Organic-rich mudrocks (ORM) from the Brushy Canyon Formation in west Texas were deposited in the Middle Permian during the Guadalupian epoch in the Delaware Basin. Brushy Canyon ORM were examined for Re-Os isotope systematics with a goal of constraining their depositional age, the 187Os/188Os value of seawater at their time of deposition, and to examine how Re and Os partition into organic material in ORM. For these samples, Rock-Eval pyrolysis data (HI: 228-393 mg/g; OI: 16-51 mg/g) indicates predominantly Type II marine kerogen with minor contributions of Type III terrestrial organic matter. Rhenium and osmium abundances correlate positively with HI, and negatively with OI, which are proxies for organic matter type and degree of preservation. These data are consistent with previous work that indicates Re and Os abundances are controlled by the availability of chelating sites in the kerogen. Brushy Canyon Formation samples have (total organic carbon) TOC values between 0.97 and 4.04% and show a strong positive correlation with both Re and Os abundances, consistent with correlations between these parameters in other ORM suites. The positive slopes in these correlations are distinct between marine (higher slopes) and non-marine (lower slopes) lacustrine environments of deposition. The Brushy Canyon’s steep slopes are consistent with marine deposition of its organic matter and an open-ocean non-restricted setting. The relationship to other Re-Os and TOC data sets appears to be a function of the restrictivity of marine conditions, and associated variations in reducing conditions during ORM accumulation of the Delaware Basin compared with more restricted lacustrine basins with local drawdown of Re and Os.
The Re-Os isotope systematics of ORM from the Brushy Canyon Formation yields a Model 1 age of 261.3 ± 5.3 Ma (2.0% age uncertainty; MSWD = 0.82). Within the uncertainty, this agrees with the expected Guadalupian age for this formation. This Re-Os age represents the first direct, absolute age for Guadalupian organic matter in the Delaware Basin. The initial (187Os/188Os)i = 0.50 ± 0.06 obtained by isochron regression represents the 187Os/188Os of seawater at this time. This value is significantly less radiogenic than modern day seawater (~1.06). The lower 187Os/188Os of Guadalupian seawater recorded is likely caused by a decrease in the relative flux of radiogenic Os from continental weathering due to a number of local and global climatic and tectonic changes that were occurring during this time.
Induced polarization effects have been seen since the 1970s in ground EM data and in airborne EM data since the 1990s. These effects normally manifest themselves as negative amplitudes in transient electromagnetic data. For fixed-wing towed-bird electromagnetic systems, negatives can also occur as a geometric effect, but for systems where the transmitter is effectively coincident with the receiver, Weidelt has shown that coincident-system negatives can only be explained as an induced polarization effect. These negatives are now being seen more frequently in airborne data as the systems have become more powerful and fly closer to the ground. Previous studies showed that the negatives are largest and most evident when the current induced in the ground is strong, but decays away quickly and the ground has a significant chargeability. These conditions have been satisfied in permafrost conditions, over lakes, over kimberlites, and near to disseminated mineralization. Identifying induced polarization effects where negatives do not occur is challenging: it can be done by analyzing the decay rate, or as I describe in this paper by looking at reversals in the shape of the response in combination with the decay rate.
Presentation Date: Wednesday, October 19, 2016
Start Time: 1:30:00 PM
Location: Lobby D/C
Presentation Type: POSTER
Operators have successfully drilled horizontal wells to make unconventional plays profitable. The next step is to drill extended-reach laterals to maximize the profitability of each well. Not only are longer laterals difficult to drill, they can be challenging to complete economically. The specific problem this paper discusses is the completion method of an extended lateral with a low bottomhole pressure. The standard completion method in unconventional plays requires post-fracturing intervention in the form of drillouts, using fracturing plugs or ball-actuated frac sleeves.
Coiled tubing-actuated fracturing sleeves offer a new completion method that eliminates the need for post-fracturing intervention. These sleeves have been used in the United States due to their ability to enable operators to obtain an unlimited number of single-entry targeted fractures while not adding ID restrictions or more post-fracturing intervention.
Large-bore fracturing plugs are also a new completion method that eliminates the need for post-fracturing intervention. These fracturing plugs enable operators to use their current plug-and-perforate method without the need to drill out before production is started. The plugs can also be deployed to great depths that coiled tubing cannot reach, making them extremely useful in extended-reach laterals.
This paper will review the hybrid stimulation method used to complete an extended-reach lateral of over 10,000 ft. with a challenging well geometry. The completion consisted of seven plug-and-perforate stages and 32 coiled tubing-actuated fracturing sleeves, providing an interventionless completion.
For a mine section comprising 100 different stoping activities, there are ~10158 different possible stoping sequences to explore in the mine schedule optimization search and this figure is indicative of the challenge posed in maximising profitability through mine schedule optimization. Any viable excavation timetable must satisfy all conditions that will constrain feasible sequences. In general, consideration of additional constraint will tend to reduce profitability. Geomechanical constraints on mine schedules, introduced with the aim of avoiding excavation instabilities, can be established for underground mine schedule optimization processes but, currently, this is done only rather crudely; precedence relations between excavation activities (stoping or development) are encoded to produce particular stope sequence patterns (e.g. ‘chevron’ or pyramidal sequences).
The work reported aimed to investigate automated processes for formulation of such geomechanical constraints. The timetable optimization approach to the problem precipitated a fresh look at time dependent, and excavation sequence dependent, deformation. Abundant evidence emerged that supported the notion that any methodology developed that failed to account for such time and sequence dependencies was itself bound to failure. Yet, it was also recognised that any deviation at all from an assumption of linear elasticity for geomechanical numerical modeling, adopted to inform geomechanical constraint formulation, would rapidly lead to impractical levels of computational effort.
Thus the approach presented here represents a compromise: the elastic stress fields induced by individual mining activities are computed for each activity, independently considered within a computational domain identical to that of all other activities. These are stored in a database. Instability risk for a specific sequence of mine activities can be assessed through superimposition of stress fields drawn from the pre-computed database. Time stamps allocated to events corresponding to the excavation processes permit the conversion of the sequence of elastic stress fields into a time table of stress fields. For specific locations within the computational domain, the aggregate effect of the sequence of mine activities leads to stress-time histories having a castellated appearance, a result of the near instantaneous response of an elastic medium to the excavation perturbations. Time dependent deformation responses are crudely allowed for through the re-profiling these castellated histories through graphical construction of curved responses, where the curve gradients are related to a viscous parameter. Such curves form the basis for a geomechanical constraint formulation to be adopted for mine schedule optimization.
To support the renewed interest in the hydrocarbon potential of the Labrador Sea, we have completed a regional seismic interpretation and integrated this with new biostratigraphic data, based on analyses of palynomorphs from wells in the Hopedale and Saglek basins. By integrating the two data-sets, we have developed a modified model for the evolution of the Labrador Margin. Our results are summarized in a tectonostratigraphic chart, which displays new and consistent age control for the major lithostratigraphic units and relates their depositional history to tectonic forces and global sea-level. Although we have identified and dated six regional unconformities in the wells, we can recognize several others on the seismic data. The older unconformities are related to the tectonics of rifting and seafloor spreading, and may delineate the onset of different stages of the rift process. In the Paleocene-Early Eocene, another significant influence was the episodic volcanism due to the passage of the proto-Iceland hot spot to the north, and to a major change in spreading direction in the Labrador Sea. During the post-seafloor spreading stage the effects of mass wasting and slumping, and of paleoenvironmental controls on the stratigraphy were more pronounced. We discuss the petroleum potential of the Hopedale Basin in terms of the structures we see on the seismic data, and highlight the Bjarni Formation, which appears to contain the most likely source and reservoir rocks.