Relative to conventional 4D flow, 4D spiral flow achieves substantial reductions in both the TE and scan times; therefore, utility for it should be sought in a variety of in vivo and complex flow imaging applications.
Background: Single V enc 4D flow MRI with Cartesian readout is hampered by poor velocity resolution and noise when imaging during diastole. Dual V enc acquisitions typically require the acquisition of two distinct datasets, which leads to longer scan times. Purpose/Hypothesis: To design and develop a 4D Spiral Dual V enc sequence. The sequence allows for separate systolic and diastolic V enc s as part of a single acquisition with a prescribed switch time. The implemented sequence was hypothesized to be comparable to Cartesian 4D flow, but with increased velocity resolution in the diastolic phase and with better scan efficiency and reduced noise. Study Type: Prospective. Population: The studied populations were two phantoms-a straight pipe with a stenotic narrowing and a phantom of the aortic arch which included a calcific polymeric valve-under both steady and pulsatile flows, six healthy volunteers, and eight patients with severe aortic stenosis (AS). Field Strength/Sequence: 1.5T, Dual V enc 4D flow with spiral readouts. Assessment: Data from the proposed sequence were compared with data from 4D Cartesian Dual V enc and Single V enc acquisitions. Noise was assessed from the acquired velocity data with the pump turned off and by varying V enc. Steady acquisitions were compared to the proximal slice of the lowest Single V enc acquisition.
A cardiac phantom can be of crucial importance in the development and validation of ultrasound and cardiac magnetic resonance (MR) imaging and image analysis methods. A biventricular multimodal cardiac phantom has been manufactured in-house that can simulate normal and pathologic hearts with different degrees of infarction. The two-chamber structure can simulate the asymmetric left ventricular motion. Poly Vinyl Alcohol (PVA) is utilized as the basic material since it can simulate the shape, elasticity, and MR and ultrasound properties of the heart. The cardiac shape is simulated using a two-chamber acrylic mold. An additional pathologic heart phantom has been built to simulate aneurysm and infarction. Segmental dyskinesis is modeled based on three inclusions of different shapes and different degrees of elasticity. The cardiac elasticity is adjusted based on freeze-thaw cycles of the PVA cryogel for normal and scarred regions.
Summary In a deepwater west African field, the relatively small number of high-cost, highly productive wells, coupled with a high barium sulfate scaling tendency (upon waterflood breakthrough of injected seawater) requires effective scale management along with removal of near-wellbore damage in order to achieve high hydrocarbon recovery. The nature of the well-completion strategy in the field (frac packs for sand control) had resulted in some wells with higher than expected skin values owing to drilling-fluid losses, residual fracture gel, fluid loss agents, and fines mobilization within the frac packs. The paper will present how the challenges of managing impaired completions and inorganic scale forced innovation in terms of when to apply both stimulation and scale-inhibitor packages to deepwater wells. This paper will outline a novel process for non-conventional batch chemical applications where bullhead stimulation treatments have been displaced deep into the formation (>20 ft) using a scale inhibitor overflush. Not only does this benefit the stimulation by displacing the spent acid and reagents away from the immediate wellbore area, but the combined treatment provides a cost savings with a single mobilization for the combined treatment. The paper will describe the laboratory testing that was performed to qualify the treatments. The four field treatments that were performed demonstrate how these coupled applications have proven very effective at both well stimulation/skin reduction and scale-inhibitor placement before and after seawater breakthrough. The term “squimulation” is used by the local operations team to describe this simultaneous squeeze-and-stimulation process. Many similar fields are currently being developed in the Campos basin (Gulf of Mexico) and west Africa, and this paper presents a good example of best-practice sharing from another oil basin.
In a deepwater West African field the relatively small number of high-cost, highly productive wells, coupled with a high barium sulfate scaling tendency (upon waterflood breakthrough of injected seawater) requires effective scale management along with removal of near-wellbore damage in order to achieve high hydrocarbon recovery. The nature of the well completion strategy in the field (frac packs for sand control) had resulted in some wells with higher than expected skin values due to drilling fluid losses, residual frac gel, fluid loss agents, and fines mobilization within the frac packs. The paper will present how the challenges of managing impaired completions and inorganic scale forced innovation in terms of when to apply both stimulation and scale inhibitor packages to deep water wells. This paper will outline a novel process for non-conventional batch chemical applications where bullhead stimulation treatments have been displaced deep into the formation (>20ft) using a scale inhibitor overflush. Not only does this benefit the stimulation by displacing the spent acid and reagents away from the immediate wellbore area, but the combined treatment provides a cost savings with a single mobilization for the combined treatment. The paper will describe the laboratory testing that was performed to qualify the treatments. The four field treatments that were performed demonstrate how these coupled applications have proven very effective at both well stimulation/skin reduction and scale inhibitor placement prior to and after seawater breakthrough. The term "squimulation" is used by the local operations team to describe this simultaneous squeeze and stimulation process. Many similar fields are currently being developed in the Campos basin, Gulf of Mexico, and West Africa, and this paper is a good example of best-practice sharing from another oil basin.
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