This paper summarizes applications of optic fiber (OF) distributed temperature sensing (DTS) technology for hydraulic fracturing stimulation diagnostics and well performance evaluation in unconventional gas well completions. Results are presented for temporary "call-out" deployments, velocity string installations, and permanent "behind casing" installations in vertical and horizontal wellbores. It is demonstrated that OF-DTS enables quantitative inflow distribution measurement for well performance evaluations in commingled multiple interval completions. OF-DTS is also shown to demonstrate the near wellbore dynamic placement characteristics during hydraulic fracture stimulation operations and, in one example, enables a superior volume distribution evaluation than radioactive (RA) tracer surveys. OF-DTS is demonstrated to be complimentary to RA tracer surveys in some cases. Additionally, this technology is being applied successfully for validation of hydraulic fracture containment in disposal well injection applications. Introduction Optic fiber distributed temperature sensing (OF-DTS) technology has been used successfully for inflow, outflow, injection, and stimulation diagnostics in oil production wellbores1–13. Shell Exploration and Production Company (SEPCo or Shell) initiated a research and development project in 2002 to develop diagnostic capabilities for unconventional gas applications. This paper presents results from evolutionary field trial installations that demonstrate quantitative inflow distribution measurement for well performance evaluations in commingled multiple interval completions, dynamic placement characteristics and a volume distribution evaluation during propped hydraulic fracturing stimulations in horizontal / vertical wellbores and disposal injection operations, and regulatory validation of hydraulic fracture containment in a disposal well injection application. Examples are presented for vertical well inflow distribution measurement applications, a horizontal well stimulation diagnostics application, a vertical well stimulation diagnostics application, and a vertical well disposal injection distribution measurement application. The quantitative inflow distribution measurement examples in this paper are for relatively dry gas systems (Liquid/Gas Ratios, LGR ~ 20 bbl/MMscf). More trials need to be conducted for higher LGR environments. Vertical Well Inflow Distribution Measurement Application Vertical Well Inflow Distribution Measurement was the initial opportunity that was pursued to evaluate if we could quantify inflow profile from temperature alone in relatively dry gas systems (LGR ~ 20 bbl/MMscf). We began by evaluating spinner rates with inflow rate calculations from production logging tool (PLT) temperature response in three wells at Pinedale Anticline. The results from this evaluation were encouraging, as illustrated in Figures 1 and 2, and provided justification for OF-DTS field trials. The interpretation methodology is described in SPE 103097 14.
It is now well established that the production from horizontal wells completed via hydraulic fracture stimulations (fracs) is highly variable along the length of the wellbore. In addition to subsurface conditions, elements of the completion design, such as fluid volume, proppant tonnage, rate, stage length, the number of perforation clusters and their spacing, influence the performance of individual stimulated intervals and wells. Information about completion efficiency can be obtained using Fiber Optic (FO) diagnostics. Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS) provide great insights into the factors controlling frac construction and performance of each perforation cluster. The integrated analysis of DAS and DTS in horizontal wells completed with multiple perforation clusters per stage indicate that, although most perforation clusters receive fluids during the stimulation, there are significant changes in efficiency during the frac stimulation process that can impact frac connectivity, conductivity and ultimately, their production. This presentation illustrates recent observations about Perforation Cluster Efficiency (PCE) using FO diagnostics and summarizes the results for many wells with Cemented Plug and Perforated completions Limited Entry design (CPnP LE).
It is a great challenge to divert acid into untreated zones in a thick, heterogeneous, and high permeability sandstone formation. The heterogeneity can be created by hydraulic fracturing, acidizing, or the nature of the reservoir. Common diverting agents do not work well in these situations. In high permeability porous media, foam has the tendency to segregate, gaseous phase will occupy smaller pores while the aqueous phase occupies the larger pores1. Due to the relative permeability effect, the higher permeability streaks becomes the preferable path for acid treatment fluids2. Therefore, limited effective diversion can be achieved by foam. Other diverting agents rely on particulate matter or polymer solution to plug off thief zones temporarily. However, the invasion of the undissolved particles and polymer residue can cause further formation damage. Owing to its rheological properties, and its lack of solids, Visco-Elastic-Surfactant diverting agents (VESDA) have been proven to be effective for acid diversion in carbonate formations3, where large flow channels are generated due to acid-rock reaction. This current study extends the application into diversion in high permeability, highly heterogeneous sandstone formations. Throughout this paper, the term VESDA is used to refer to the VES diverting agent. Laboratory tests have shown that VES is capable of increasing the flow resistance in the high permeability rock (simulated by a proppant pack) and will divert treatment fluid into the low permeability sandstone matrix. The process was more efficient if multiple stages of alternating VES and acid were used. Field case histories in Gulf of Mexico are also presented in this study to demonstrate the effectiveness of the VES material for acid diversion in the highly permeable and heterogeneous sandstone reservoirs. Introduction When a well penetrates through multiple zones in a heterogeneous reservoir, it is difficult to treat all of the zones evenly during matrix acidizing. Job design and fluid selection need to be made by considering the permeability contrast, saturation4 in the formation, and availability of the material. On deep water offshore platforms, the problem is further complicated by the space constraint and transportation of the chemicals. Commonly used diverting agents include polymer gels, foams, oil soluble solids materials5, and rock salt. These materials either require more complex process, such as foam, or fail to reach the full stimulation potential due to damage induced by residue precipitation, saturation alteration, or solid invasion. VESDA overcomes these difficulties by providing a easy, effective, and clean solution to the acid diversion process. Reservoirs in the deep water of the Gulf of Mexico are normally completed by gravel pack or frac-n-pack, due to their sand producing tendency. Frequently, a fluid loss control pill is required during well completion operations after perforating. Therefore, before gravel pack or frac-n-pack, a matrix acidizing job will be performed to cleanup up the remaining drilling, perforating, and pill damage. Because of the high permeability of these formations, acid diversion is a challenging task. Foam segregation can cause the acid to preferentially enter the higher permeability layers, leaving the formation partially treated. Solid-containing diverting agents can invade into the matrix causing additional damage. This defeats the purpose of acidizing treatment. The VESDA possesses the unique characteristic of being more viscous in the aqueous phase and non-viscous in the hydrocarbon phase. When it enters the acid treated zone, which is fully saturated by an aqueous phase (acid) near the wellbore, its viscosity becomes a resistance to the following treating fluid. Thus the treating fluid has to enter the zones that are still highly saturated by hydrocarbon. The VESDA also cleans up easily without leaving any residue upon contacting liquid hydrocarbon during flow back. Hence the full benefit of the acid stimulation can be achieved.
Field trials of new methodologies, products or technologies are considered to be an effective way to gauge the true value of such innovations. However it is difficult and expensive to conduct a rigorous field trial, especially in tight, multi-layered reservoirs, and proper design and analyses are critical to accurately interpret the results. In multi-layered reservoirs the production from individual frac stages must often be evaluated with production logs - this additional expense accentuates the need to carefully design the field trial and thoroughly analyze the resulting data to extract as much value as possible. This paper will provide a detailed comparison of well productivity in the Pinedale Anticline as a function of proppant type and subinterval. Well production has been normalized by many parameters, including reservoir kh, kh?P, kh*(Pr2-Pf2), Fh, and also compared by well location to determine the degree to which those techniques provide similar conclusions. In addition to describing how these field results influence proppant selection in the Pinedale Anticline, this paper will describe many aspects of field trial planning, as well as the proper handling of data to assist in the design of future trials. This paper will review the following topics: The results of this study will also be compared to other published field trials to examine well populations, data consistency, and to assess whether studies in similar reservoirs carry similar findings. This paper will summarize the conclusions that are consistent between numerous tight gas field studies in the region, and highlight changes to fracture treatments which have consistently improved well productivity and profitability in these reservoirs. Introduction In many ways, a field trial resembles a legal court trial. Evidence must be carefully examined, and opposing arguments should be considered. Individual pieces of information are seldom 100% convincing; conclusions must be reached from layers of supporting evidence. The jury must decide the verdict based on the confidence in the evidence, and various risk thresholds may be applied (" the preponderance of evidence" or "beyond a reasonable doubt"). One advantage to a field trial is that it can be carefully designed to eliminate or reduce the effect of some variables that could influence the results. This paper will describe the design and analyses of a field trial in the Pinedale Anticline and summarize the supporting evidence the jury may use to select proppant in this field. Background Information During the past five years, the industry has completed over 200 wells in the Pinedale Anticline (PDA), utilizing over 500 million pounds of proppant. However, there is no consensus on the optimal stimulation design, with each operator using different criteria to select proppant. This trial was specifically designed to determine which proppant was most cost-effective in wells completed by Shell Rocky Mountain Production. Design of Field Trial This study compares the production from 446 fracture treatments in 30 new wells completed by Shell between September 2001 and September 2004. During this time, efforts were made to maintain a consistent stimulation design to determine the impact of proppant selection upon stage production and profitability.
The use of Distributed Acoustic Sensing for Strain Fronts (DAS-SF) is gaining popularity as one of the tools to help characterize the geometries of hydraulic fracs and to assess the far-field efficiencies of stimulation operations in Unconventional Reservoirs. These strain fronts are caused by deformation of the rock during hydraulic fracture stimulation (HFS) which produces a characteristic strain signature measurable by interrogating a glass fiber in wells instrumented with a fiber optic (FO) cable cemented behind casing. This DAS application was first developed by Shell and OptaSense from datasets acquired in the Groundbirch Montney in Canada. In this paper we show examples of DAS-SF in wells stimulated for a variety of completion systems: plug-and-perforating (PnP), open hole packer sleeves (OHPS), as well as, data from a well completed via both ball-activated cemented single point entry sleeves (Ba-cSPES) and coil-tubing activated cemented single point entry sleeves (CTa-cSPES). By measuring the strain fronts during stimulation from nearby offset wells, it was observed that most stimulated stages produced far-field strain gradient responses in the monitor well. When mapped in space, the strain responses were found to agree with and confirm the dominant planar fracture geometry proposed for the Montney, with hydraulic fractures propagating in a direction perpendicular to the minimum stress. However; several unexpected and inconsistent off-azimuth events were also observed during the offset well stimulations in which the strain fronts were detected at locations already stimulated by previous stages. Through further integration and the analysis of multiple data sources, it was discovered that these strain events corresponded with stage isolation defects in the stimulated well, leading to "re-stimulation" of prior fracs and inefficient resource development. The strain front monitoring in the Montney has provided greater confidence in the planar fracture geometry hypothesis for this formation. The high resolution frac geometry information provided by DAS-SF away from the wellbore in the far-field has also enabled us to improve stage offsetting and well azimuth strategies. In addition, identifying the re-stimulation and loss of resource access that occurs with poor stage isolation also shows opportunities for improvement in future completion programs. This in turn, should allow us to optimize operational decisions to more effectively access the intended resource volumes. These datasets show how monitoring high-resolution deformation via FO combined with the integration of other data can provide high confidence insights about stimulation efficiency, frac geometry and well construction defects not available via other means.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.