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Pictures shot in fractured wells show how a high-pressure slurry of water and sand carves up the perforations. This paper presents the evolution of a Bakken advanced completion design with the added enhancement of extreme limited entry (XLE) perforating. With this strategy, an operator has consistently stimulated more than 11 perforation clusters per stage. Good reservoir detective work costs money, but two studies show how it can help identify even more expensive problems. Significant production gains are being made with hydraulicly fractured wells using diversion to stimulate a higher percentage of the perforations.
Because of inherent complexities, understanding the characteristics of perforations in downhole environments is a significant challenge. Perforation-flow laboratories have been used to provide insight into cleanup and productivity mechanisms around perforation tunnels. Completion engineers feel pressure to maximize production per acre and minimize the downsides of fracturing in tight spaces. Terry Palisch, talks about promoting knowledge sharing as part of JPT’s tech director report. An advisor at Schlumberger discusses the company’s work in examining the effect of perforations on hydraulic fracture initiation.
Workover operations in shallow low pressure heavy oil unconsolidated sandstone reservoir in Kuwait presents a major challenge due to significant killing fluid loss which causes wellbore plugging, incremental operational costs due to more rig days, excess brine volumes, and more importantly the impact of deferred production due to formation damage. This paper presents an innovative fluid-loss control pill added to killing fluids, which has resulted in significant cost savings and well productivity improvements.
The subject heavy oil reservoir have formation pressure equivalent to 6.3 PPG versus 9.3 PPG Potassium Chloride brine used as killing fluid. This overbalance condition is a requirement as safety barrier but conversely it leads to hundreds of barrels of killing fluid losses with the consequently invasion and formation damage. Kuwait Oil Company recently added a new customized fluid loss control pill of high purity vacuumed dried evaporated salt to the well killing procedure. Using this fluid loss control pill both drilling and reservoir engineers achieved their aim in terms of safety operation and no formation damage.
To test this new pill, two shallow wells with 220 psi reservoir pressure and perforation set at 630 ft were selected to record the losses. The first well had undergone workover including recordings from caliper, cement, and ultrasonic logs, which measured the positive impact of the new control pill on logs quality by excluding fluid pumping while logging and having constant fluid level at surface, which saved cable head from unnecessary tensions. In a second well, there was hanged standalone screen on a packer against the perforation and there is no direct access to the perforation. The control pill was customized to be pumped into the screen, which sealed the screen itself perfectly. The control pill flowed back easily in both wells and same loss rate was observed after removing the pill, which confirmed no negative impact on reservoir permeability.
KOC confirmed that the two jobs were successful and the pill to be approved for full field implement in other operations. The achieved success criteria summarized as follows: Hydrostatic column is a safety barrier that assuring fluid level at surface during workover is safety requirement especially in high Gas oil ratio wells. Full circulation enhances sand cleanup operation. Fluid level at surface results in accurate logging by eliminating invasion into reservoir and support improved operations.
Hydrostatic column is a safety barrier that assuring fluid level at surface during workover is safety requirement especially in high Gas oil ratio wells.
Full circulation enhances sand cleanup operation.
Fluid level at surface results in accurate logging by eliminating invasion into reservoir and support improved operations.
Hosseini, Seyed Abolhassan (RGL Reservoir Management Inc., University of Alberta) | Roostaei, Morteza (RGL Reservoir Management Inc.) | Velayati, Arian (University of Alberta) | Soroush, Mohammad (RGL Reservoir Management Inc., University of Alberta) | Mohammadtabar, Mohammad (RGL Reservoir Management Inc., University of Alberta) | Mahmoudi, Mahdi (RGL Reservoir Management Inc.) | Fattahpour, Vahidoddin (RGL Reservoir Management Inc.)
Erosion of standalone screens in thermal wells can lead to significant damage and reduction in production. The dominant failure mechanism is the development of localized high-velocity hot spots in the screen due to steam breakthrough or flashing of the steam across the screen. This study provides methods to assess the erosion potential of screen material devices to determine the allowable production conditions which avoid erosion.
In this study the effects of impact angle, flow rate, sand concentration, particle size, and fluid viscosity on erosion are systematically investigated through a multivariable study. Experimental impingement testing is performed on screens in different orientations. Erosion is accessed by collecting weight loss data of the screen. Empirical erosion models are calibrated to provide predictions of functional relationships between erosion rate and varied parameters. Computational Fluid Dynamic (CFD) simulations are performed prior to the experimental work to visualize particle flow paths through the screen and determine local flow and impact velocities and wear patterns.
The performance of five existing erosion models is assessed through experimental testing of sand control screens. In order to translate short-term, high-velocity laboratory test results into field erosion predictions, an empirical erosion model is then developed and employed to provide well flow guidelines and minimize erosion potential. This suggests that the use of erosion prediction models in situations in which due to lack of time/data tuning is not possible, may still provide a reasonable estimate for the rate of material loss of the screen. The model is used to obtain threshold superficial velocity curves for several conditions.
The main concern associated with existing erosion models is that they do not consider sand production, nor do they account for many other factors that affect erosion process. An erosion model, coupled with CFD simulation, has been developed, that account for factors such as geometry, size, material, fluid properties and rate, sand size, shape, and density in downhole flow conditions.
This paper introduces a 3D hydraulic fracturing propagation model (3D-HFPM) for evaluating fracture extension, geometry, stress response, fracture spacing, and potential for refracturing. The model is illustrated with data of the Horn River shale of Canada.
The model is developed using a combination of finite element method (FEM) and boundary element method (BEM) for evaluating fluid-flow, fracture deformation, and stress change in the reservoir. The model is calibrated using a limited amount of microseismic observations and recreate the fracture network when microseismic data are unavailable.
An adapting meshing algorithm is incorporated to improve the capacity of the model to handle large and complex fracture networks such as the ones found in low permeability reservoirs.
The continuity of fracture propagation and fluid leak-off during stimulation may be high enough to connect different production intervals and to create interference between stages, especially in wells with small path fracture spacing and multi-level completions.
The comparison between the propagation model and microseismic data shows good agreement as the number of events increases as the fracture propagates into the reservoir. However, using only microseismic data to calculate the extension of the hydraulic fracture results in an overestimation of the fracture length.
The model quantifies the altered stress zone, which is helpful to determine possible fracture reorientation and spacing. The evaluation of stress shadow and fracture reorientation reveals the advantages of refracturing using new over old perforations. The operation restores fracture conductivity and increases the fracture network as well as the drainage areas leading to an economic operation.
The model improves the characterization of the Stimulated Reservoir Volume (SRV) in tight and shale reservoirs in those cases where microseismic data are scarce. Furthermore, the model is a viable tool for evaluating potential refracturing candidates.
A suite of production logs can help to determine the fraction of total production contributed by different perforated intervals. This well produces gas from four perforated intervals; however, the bottom two intervals are in such close proximity that they are considered as one perforation set. The well produces 175 to 320 Mscf/D, with negligible water production. The objective of the production logs was to determine the fraction of total production contributed by each perforation set. With the well flowing, fluid density, temperature, and continuous-spinner flowmeter profiles were recorded.
Fluid capacitance logging is used to distinguish the mix of water and hydrocarbons in the wellbore fluid. The fluid-capacitance-logging tool includes an inside dielectric probe located on the tool's axis. The probe is surrounded by an outside housing that is open to the wellbore fluid. Together, the probe, the housing, and the fluid constitute an electrical capacitor, the capacitance level of which depends on the particular fluid, or fluids, within the capacitor. Circuitry within the tool is connected to the electrical capacitor, with the result that the circuitry generates an oscillating signal that varies inversely with the capacitance level.
The radioactive tracer-logging tool has a reservoir to hold radioactive material and a pump section at the top. For injection-well logging, two gamma ray detectors below the reservoir and pump are preferable. Some tools employ only one detector, but this is less desirable. The tool includes the circuitry to amplify and transmit the detector counts to the surface, for recording. Most natural radioactivity underground is from the decay of isotopes of potassium, thorium, and uranium.
The following sections describe operating principles for each of the tools listed in Table 4.1. The text will indicate applications for which a tool is best suited, those for which it is only partially suited and, when possible, those for which a tool is not suitable. Some interpretive principles and recommended logging procedures will be presented in examples. However, the reader should refer to the Appendix for detailed information of this type. Oxygen-activation, cement-bond, and casing-inspection tools are not treated. These tools are, however, included in the application tables of the Appendix.
Introduction Perforating is a process used to establish a flow path between the near reservoir and the wellbore. It normally involves initiating a hole from the wellbore through the casing and any cement sheath into the producing zone. The effectiveness of this process depends on the care and design of the perforating procedure. Because a high percentage of current wells use a cased-hole completion, the importance of the design and application of the perforating process cannot be overstated. Perforations are an elemental piece of the inflow section of the well and have significant impact on the total completion efficiency. This chapter describes the methods of creating the best flow path for a particular completion. It also contains information on completion diagnostics and candidate selection for situations in which reperforating could improve production. The intent of this chapter is to familiarize the engineer with methods and techniques to improve the flow path, not all of which involve perforating equipment. Establishing an optimum flow path requires the execution of a number of critical steps. These critical operations are identified throughout the chapter and are used in design, quality control inspection, and quality control. A brief description is needed of the alternative completion methods to cased, cemented, and perforated completions. Openhole completions offer several options that should not be ignored in a quest for a high efficiency flow connection to the reservoir.