Conventional Stimulation Techniques Research Articles

Long-Term Continuous Cervical Spinal Cord Stimulation Exerts Neuroprotective Effects in Experimental Parkinson's Disease.

BackgroundSpinal cord stimulation (SCS) exerts neuroprotective effects in animal models of Parkinson’s disease (PD). Conventional stimulation techniques entail limited stimulation time and restricted movement of animals, warranting the need for optimizing the SCS regimen to address the progressive nature of the disease and to improve its clinical translation to PD patients.ObjectiveRecognizing the limitations of conventional stimulation, we now investigated the effects of continuous SCS in freely moving parkinsonian rats.MethodsWe developed a small device that could deliver continuous SCS. At the start of the experiment, thirty female Sprague-Dawley rats received the dopamine (DA)-depleting neurotoxin, 6-hydroxydopamine, into the right striatum. The SCS device was fixed below the shoulder area of the back of the animal, and a line from this device was passed under the skin to an electrode that was then implanted epidurally over the dorsal column. The rats were divided into three groups: control, 8-h stimulation, and 24-h stimulation, and behaviorally tested then euthanized for immunohistochemical analysis.ResultsThe 8- and 24-h stimulation groups displayed significant behavioral improvement compared to the control group. Both SCS-stimulated groups exhibited significantly preserved tyrosine hydroxylase (TH)-positive fibers and neurons in the striatum and substantia nigra pars compacta (SNc), respectively, compared to the control group. Notably, the 24-h stimulation group showed significantly pronounced preservation of the striatal TH-positive fibers compared to the 8-h stimulation group. Moreover, the 24-h group demonstrated significantly reduced number of microglia in the striatum and SNc and increased laminin-positive area of the cerebral cortex compared to the control group.ConclusionsThis study demonstrated the behavioral and histological benefits of continuous SCS in a time-dependent manner in freely moving PD animals, possibly mediated by anti-inflammatory and angiogenic mechanisms.

Reduced muscle fatigue using kilohertz-frequency subthreshold stimulation of the proximal nerve

Objective. Conventional electrical stimulation techniques targeting the motor points often induce early muscle fatigue onset that can limit clinical applications. In our current study, we evaluated the muscle activation and force generation during fatigue using a novel stimulation technique. Approach. Clustered subthreshold 80 μs current pulses at 10 kHz (high-frequency mode, HF) were delivered transcutaneously to activate the median and ulnar nerve bundles and induce dispersed activations of motor units. Conventional stimulation technique with 800 μs pulses at 30 Hz (low-frequency mode, LF) served as a control condition. Fatigue was evoked by delivering the stimuli continuously for 5 min, with matched initial contraction force (approximately 30% of maximal voluntary contraction) between the HF and LF modes. The elicited finger flexion forces and the muscle activation patterns quantified by high-density electromyogram (EMG) from the finger flexor muscles were compared. Main results. Our results revealed that the elicited force was prolonged under the HF stimulation mode, manifested as a slower decay of the force, a smaller absolute force decline, a higher force plateau, and a larger force-time integral, in comparison with the LF mode. The force-to-EMG ratio under the HF stimulation was also consistently higher than that under the LF mode. In addition, the EMG spatial distribution showed that the muscle activation tended to be more spread-out under the HF mode compared with the LF mode. These results indicated that the HF stimulation induced a higher efficiency of muscle activation, which can potentially reduce muscle fatigue. Significance. Our findings revealed that the subthreshold kilohertz nerve stimulation can induce temporally and spatially dispersed activation of different motor units with more efficient activation patterns. The reduced muscle fatigue can have a prominent advantage in neural rehabilitation involving transcutaneous electrical nerve stimulations.

Improved muscle activation using proximal nerve stimulation with subthreshold current pulses at kilohertz-frequency

Objective. Transcutaneous electrical nerve stimulation can help individuals with neurological disorders to regain their motor function by activating muscles externally. However, conventional stimulation technique often induces near-simultaneous recruitment of muscle fibers, leading to twitch forces time-locked to the stimulation. Approach. To induce less synchronized activation of finger flexor muscles, we delivered clustered narrower pulses to the proximal segment of the median and ulnar nerves at a carrier frequency of either 10 kHz (with an 80 µs pulse width) or 7.14 kHz (with a 120 µs pulse width) (high-frequency mode, HF), and different clustered pulses were delivered at a frequency of 30 or 40 Hz. Conventional stimulation with pulse frequency of 30 or 40 Hz (low-frequency mode, LF) was used for comparison. With matched elicited muscle forces between the HF and LF modes, the force variation, the high-density electromyogram (EMG) signals recorded at the finger flexor muscles and stimulation-induced-pain levels were compared. Main results. The compound action potentials in the 10 kHz HF mode revealed a significant difference (i.e. a lower amplitude and area, and a wider duration) compared with the LF mode, indicating cancellations of asynchronized action potentials. A smaller fluctuation in the elicited forces in the 10 kHz mode further demonstrated the less synchronized activation of different motor units. These effects tended to be weaker in the 7.14 kHz HF condition. However, the levels of pain sensation was not reduced in the HF mode potentially due to the high charge density used in the HF mode. Our findings indicated that different nerve fibers were recruited asynchronously through summations of different numbers of subthreshold depolarizations in the HF mode. Significance. Compared with the LF mode, the HF mode stimulation was capable of activating the nerve fibers in a less synchronized way, which is more similar to the physiological activation pattern.

No need for luteal phase support in IVF cycles after mild stimulation: proof-of-concept study

This is a pilot study performed in a private IVF unit. The objective of the study was to investigate whether luteal support is required in IVF cycles after mild stimulation with clomiphene citrate and low FSH doses. The study included 15 patients with good prognosis (defined as ≤38 years old with normal ovarian reserve and normovulatory cycles, body mass index <29 kg/m2, no previous cycles, no severe endometriosis, no history of recurrent miscarriage, no endocrine/autoimmune diseases and no surgical semen extraction from the partner) undergoing IVF with mild stimulation. Patients were monitored during the luteal phase by serum progesterone and LH. The luteal support was started only when necessary. No patient needed luteal phase support because the resultant steroid environment was different from that associated with conventional stimulation techniques. The live birth rate was 40% (6/15) and the implantation rate 30% (6/20). There are several benefits to mild stimulation, including low cost, less patient distress and improved endometrial receptivity. Our study supports the concept that mild stimulation may have an additional benefit during the luteal phase, by obviating the need for luteal phase support.

New Stimulation Method Significantly Improves Hydrocarbon Recovery

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 177061, “A New Stimulation Method To Significantly Improve Hydrocarbon Recovery by Use of Temporary Beneficial Changes in Stress Anisotropy,” by B.J. Lewis and J.B. Surjaatmadja, Halliburton, prepared for the 2015 SPE Latin American and Caribbean Petroleum Engineering Conference, Quito, Ecuador, 18–20 November. The paper has not been peer reviewed. As a result of the creation of a hydraulic fracture, transient geomechanics forces are exerted on the formation, which modify the stress landscape near the wellbore and the fracture plane. It has been observed that the potential exists for temporary reversal in the minimum-stress direction, enabling a brief time interval in which a second hydraulic fracture can be created in a completely different direction. This provides hydraulic-fracturing connectivity to previously unattainable locations in the formation. This paper presents a computational validation of this multioriented hydraulic-fracturing (MOHF) process. Overview of Pinpoint-Fracturing Techniques Pinpoint fracturing, also known as pinpoint stimulation, is a general term used in the industry to refer to fracturing processes that specifically target individual treatment intervals in a multiple-interval completion. More than 20 different pinpoint-stimulation techniques have been developed for coiled-tubing- (CT) or drillpipe-deployed jetting tools. Although several mechanically actuated or explosive-perforation pinpoint methods have been developed, the most widely used pinpoint methods are hydrajet coupled stimulation procedures. This paper focuses only on the hydrajet methods and discusses how pinpoint fracturing can be applied to achieve an MOHF stimulation. The length of the wellbore being treated per stage of the operation is usually much smaller than it is with conventional stimulation techniques. Conventional methods, either sliding-sleeve or plug-and-perforate, generally treat 15 m to more than 60 m of the wellbore at a time. In contrast, with pinpoint methods, only one fracture is being initiated by the hydrajets per treatment stage; therefore, more stages are generally used than with the plug-and- perforate method. The spacing between fractures is designed to be directly related to the expected drainage potential of each fracture and may also be influenced by the unique geological features in the area. This allows for a significant flexibility in terms of the treatment design. A summary of operational benefits of pinpoint stimulation is provided in the complete paper, but they include the following: Large number of treatment intervals with only one trip into the well Reduced time to complete each treatment interval Reduced downtime between treatment intervals Fracture placement designed for each individual fracture, rather than in large treatment intervals Optimized stimulation-fluid system, pressure, and rate for every fracture As with other processes, there are some drawbacks with pinpoint stimulation compared with conventional methods. If the stimulation treatment will be tubing-conveyed, a rig or hydraulic-workover (HWO) unit would be required on location. Most pinpoint methods also require two separate pumping sources to be available (one for the tubing flow and one for the annulus flow). Therefore, additional surface flow piping and valves are necessary; however, both pumping sources contribute to the total-treatment fluid-flow rate.

GABAB receptors sharpen tuning of a sound localization circuit

GABA_B receptors sharpen tuning of a sound localization circuit

Multioriented Fracturing in Unconventional Reservoirs Offers Improved Production by Better Connectivity

Summary In the oil field, the term "unconventional" almost always means difficult to obtain for one or another reason. One reason addressed in this paper relates to formations characterized by the lack of permeable features that connect or can be easily connected to the wellbore using conventional stimulation techniques. The common logic of placing larger and larger fractures does work, but, when using this approach, the cost-to-reward ratio can be far from desirable. It is well known that placing a second fracture sometime later in the life of a well will result in a fracture that extends in a slightly different direction, mostly caused by the drainage of the fluid near the fracture face. In this situation, fracture redirection is probably caused by the pore-pressure decline near the producing fracture face. In some instances, the new fracture produces almost as if it has reached a new formation. This paper discusses placement of such second (or third) hydraulic fractures within the same time domain from the same wellbore section. While this has not yet been performed in the field, it is believed that the first fracture will modify the stress field to a perpendicular direction. Combined with the hypothesis of the hard-to-accept concept that fractures often shy away from the most-productive zones, this approach will cause the second fracture to extend directly into the more-productive zones, thus providing a substantial production boost.

Astrocyte-to-neuron signaling in response to photostimulation with a femtosecond laser

Conventional stimulation techniques used in studies of astrocyte-to-neuron signaling are invasive or dependent on additional electrical devices or chemicals. Here, we applied photostimulation with a femtosecond laser to selectively stimulate astrocytes in the hippocampal neural network, and the neuronal responses were examined. The results showed that, after photostimulation, cell-specific astrocyte-to-neuron signaling was triggered; sometimes the neuronal responses were even synchronous. Since photostimulation with a femtosecond laser is noninvasive, agent-free, and highly precise, this method has been proved to be efficient in activating astrocytes for investigations of astrocytic functions in neural networks.

Characteristics of calcium signaling in astrocytes induced by photostimulation with femtosecond laser

Astrocytes have been identified to actively contribute to brain functions through Ca(2+) signaling, serving as a bridge to communicate with neurons and other brain cells. However, conventional stimulation techniques are hard to apply to delicate investigations on astrocytes. Our group previously reported photostimulation with a femtosecond laser to evoke astrocytic calcium (Ca(2+)) waves, providing a noninvasive and efficient approach with highly precise targeting. In this work, detailed characteristics of astrocytic Ca(2+) signaling induced by photostimulation are presented. In a purified astrocytic culture, after the illumination of a femtosecond laser onto one cell, a Ca(2+) wave throughout the network with reduced speed is induced, and intracellular Ca(2+) oscillations are observed. The intercellular propagation is pharmacologically confirmed to be mainly mediated by ATP through P(2)Y receptors. Different patterns of Ca(2+) elevations with increased amplitude in the stimulated astrocyte are discovered by varying the femtosecond laser power, which is correspondingly followed by broader intercellular waves. These indicate that the strength of photogenerated Ca(2+) signaling in astrocytes has a positive relationship with the stimulating laser power. Therefore, distinct Ca(2+) signaling is feasibly available for specific studies on astrocytes by employing precisely controlled photostimulation.

Re-animation of muscle flaps for improved function in dynamic myoplasty.

The authors report on a series of experiments designed to produce a skeletal muscle contraction functional for dynamic myoplasties. Conventional stimulation techniques recruit all or most of the muscle fibers simultaneously and with maximal strength. This approach has limitations in free dynamic muscle flap transfers that require the muscle to contract immediately after transfer and before re-innervation. Sequential stimulation of segments of the transferred muscle provides a means of producing non-fatiguing contractions of the muscle in the presence or absence of innervation. The muscles studied were the canine gracilis, and all experiments were acute studies in anesthetized animals. Comparison of conventional and sequential segmental neuromuscular stimulation revealed an increase in muscle fatigue resistance and muscle blood flow with the new approach. This approach offers the opportunity for development of physiologically animated tissue and broadening the abilities of reconstructive surgeons in the repair of functional defects.

Application of Horizontal Wells to a Tight-Gas Sandstone Reservoir: A Case History

Summary The Anglia gas field is located in the southern sector of the U.K. Continental Shelf (UKCS) in Blocks 48/18b and 48/19b. The reservoir is contained within the Permian Rotliegendes sandstone and is of small to medium size by U.K. southern North Sea standards. The field is divided into an east and west area with the gas initially in place distributed equally. Appraisal-drilling results indicated that the eastern portion of the field exhibited good productivity, whereas wells drilled into the western area produced at subeconomic rates. Development studies showed that to make the field development economically viable, well rates would have to be increased in the poorer western region. Conventional stimulation techniques were explored, particularly hydraulic fracturing; however, these proved unsuccessful owing to the proximity of the water leg. Attention, consequently, focused on the then emerging technique of horizontal drilling as a means of increasing well productivity. Development of a geologic model identified that the reservoir could be zoned into six reservoir units and that to maximize productivity, placement of the well into the predominantly aeolian zones was necessary. Reservoir simulation studies showed that a minimum 70-ft stand-off from the gas/water contact (GWC) was required to maximize ultimate recovery. This paper describes the analysis methods used and the results of applying horizontal wells in the field development and shows how, at a small cost premium, the method enabled a marginal field to be developed successfully.

Backsurging and Abrasive Perforating To Improve Perforation Performance

Compared with conventional completions, backsurged completions in this group of wells on the Louisiana Gulf Coast show permanently improved productivity. To a lesser extent, abrasive perforating also improves productivity. To a lesser extent, abrasive perforating also improves well completions, particularly in zones that are less than 30 percent depleted. Introduction One of the major problems associated with conventional completion practices in unconsolidated sands is that of obtaining unimpaired perforations prior to sand control installation. Debris resulting from crushed formation material and explosion products often remains in perforations, producing severe restrictions to fluid flow. Zones that would be expected to have productivity indices of 2 to 4 B/D/psi based on permeability estimates in fact often exhibit productivity indices less than one-tenth of these values. This is particularly true in Shell's South Pass Blocks particularly true in Shell's South Pass Blocks 24 and 27 fields, where nearly all completions require sand control before sustained production can be established. Any debris remaining in perforations when sand control is installed can perforations when sand control is installed can become "locked-in," resulting in a permanent impairment that cannot be corrected by conventional stimulation techniques. Suman studied perforation debris and proposed several methods to increase perforation efficiency. We shall discuss here the effectiveness of two of those methods backsurging and abrasive perforating. The Backsurge Tool The backsurge tool consists of an atmospheric chamber formed by two valves spaced in the work string above a squeeze packer (Fig. 1). After conventionally perforating, the assembly is run and set above the perforating, the assembly is run and set above the perforations to be treated. The lower valve is then perforations to be treated. The lower valve is then opened to expose the perforations to the atmospheric pressure in the chamber. The resulting surge flows pressure in the chamber. The resulting surge flows perforating debris and crushed formation material perforating debris and crushed formation material into the wellbore where it can be reversed out or allowed to settle into the rat hole. The well is then ready for installation of a sand control. When plastic consolidation is used, the well may be treated through the tool without unseating the packer, thus the perforations need not be exposed to annular fluids until perforations need not be exposed to annular fluids until the plastic has cured. Bottom-hole pressure bombs can be run below the tool and inside the chamber to monitor pressures throughout the treatment. Backsurging was first introduced in the South Pass Block 27 field in July, 1969. Initial results were impressive, and in Dec., 1969, backsurging was adopted as a standard procedure. Through Aug., 1970, more than 80 zones had been backsurged; 70 of these are oil-producing zones on which data are complete enough to be meaningful and are included in the study. Fifty-two backsurge treatments were performed on "new" zones not previously open; 11 were performed on "new" zones not previously open; 11 were in "old" zones in which an additional interval was perforated during workover; and seven were in old perforated during workover; and seven were in old zones in which the perforated interval was not altered; i.e., seven were workovers to replace sand control. All but five new zone completions were gravel packed. These five were given sand consolidation treatments. The Abrasive-Perforating Tool The abrasive-jetting process uses sand carried in salt water or acid pumped through jetting nozzles at high velocity to abrade perforations through the casing and cement sheath. JPT P. 1207

Sandstone Continuity in the Mesaverde Formation, Rulison Field Area, Colorado

Analysis of data from an outcrop study of Mesaverde sandstone lenses showed that they could be characterized by length:thickness ratio (normal distribution, mean of 20, and standard deviation of 0.29 log cycle). A reservoir model based on these data yielded results consistent with well tests and production history. Introduction Rulison field produces gas from multiple sandstone reservoirs in the Mesaverde formation of Upper Cretaceous age. The field is believed to contain a large volume of gas but is not commercial because the wells are capable of producing only a relatively small volume of gas each day. The low rates of production are caused by the low permeability and the production are caused by the low permeability and the shape and discontinuity of the individual sandstone bodies. Rulison and other similar fields in the area are not fully developed because the wells will not repay the cost of drilling and completing. Conventional stimulation techniques have not been effective in increasing the productivity of the wells. The field is the site of a joint industry-government experiment to stimulate gas producing rates by fracturing the reservoirs with an underground nuclear explosion. This experiment, known as Project Rulison, is being conducted by Austral Oil Co., Inc., and the U. S. Atomic Energy Commission. The study reported in this paper was part of the preshot investigation of the feasibility of part of the preshot investigation of the feasibility of nuclear stimulation at Rulison field. General Geology The sequence of rocks present at Rulison field, which is located in the Piceance basin (Fig. 1), and their relation to the general stratigraphy of the area are shown on Fig. 2. Rocks ranging in age from Quaternary to Precambrian are thought to be present. The local structure at Rulison field -northeast regional dip - is not important to the gas accumulation. The entrapment of gas is stratigraphically controlled and is primarily a result of the discontinuity of the individual sandstones. The gas deposit is an aggregate of hundreds of separate small accumulations in individual discontinuous sandstone bodies. Mesaverde Formation Stratigraphy The Mesaverde formation as referred to here includes all sediments below the base of the Ohio Creek conglomerate (Paleocene) and above the top of the Mancos shale (Cretaceous). This definition is used by most geologists working in the subsurface of the area. The Mesaverde includes the stratigraphic equivalents of the Lance, Lewis, Williams Fork, and lies formations as they are recognized in outcrops around the Piceance basin. We have made no attempt to identify these formations in this study. The Mesaverde formation in Rulison field ranges in thickness from approximately 3,400 ft in the southwestern portion of the field to 3,900 ft in the northeast. It consists of a sequence of sandstones, shales and coals that were deposited near the western shoreline of a broad, shallow sea that extended north-south across the area. The varied and changing local conditions associated with the flood plain and shoreline during Mesaverde time deposited a complex sequence of rocks. These conditions also generated and preserved a large volume of gas. The gas was apparently formed and trapped at the time of deposition or shortly thereafter. JPT P. 911

New Fracture-Acid Technique Provides Efficient Stimulation Of Massive Carbonate Sections

ABSTRACT A new stimulation technique has been developed and successfully applied todeep massive carbonate completions in several areas. This same technique shouldprove useful in similar massive carbonate sections in Canada. Basically, thenew technique provides deep fracture penetration into the reservoir withlow-cost fluids and good fracture conductivity by effectively etching thefracture faces with special acid formulations. It differs from conventional hydraulic fracturing treatment only in thatacid replaces conventional propping agents. The treatment is economical in thatit uses inexpensive frac fluids to create fracture area and penetration andreduce fluid leak-off. Much smaller quantities of acid may then be used to etchthe desired conductivity at the required depth of penetration in the reservoir.If acid alone were used, the volume required would be prohibitively expensive. The new technique also eliminates many of the hazards of conventionalfracturing and acidizing. As no propping agent is used, there is no danger ofscreen-outs. Corrosion is minimized, because the pad volume of frac fluid coolsthe well equipment prior to the injection of acid. The technique, thus, is particularly useful in deep, high- temperature reservoirs. INTRODUCTION MASSIVE low-porosity, low-permeability carbonate formations such as the Ellenburger, Devonian, Hunton, Edwards, Budda and Smackover in the United States, and the Mississippian in Canada, are known to contain substantial andattractive quantities of hydro-carbons. Many of these accumulations have notresponded sufficiently to conventional stimulation techniques to warrantfurther exploration. Although a two-to three-fold productivity improvement canfrequently mean the difference between a noncommercial and commercial well, conventional acidizing and/or fracturing treatments have not provided suchincreases for sustained periods. A new dual fracturing-acidizing stimulationtechnique is now showing promise of improving productivity from these massiveformations. Basically the new fracturing technique provides deep reservoir penetrationwith low-cost fluids and good conductivity by effectively etching the fracturefaces with acid. Thus, it utilizes the advantages of both fracturing andacidizing penetration of the reservoir by the hydraulic fluids and developmentof high conductivity by acid. This treating technique also minimizes theprincipal hazards of conventional fracturing and acidizing-screen-outs andcorrosion. The combination also provides a more effective and economicalapproach to stimulation with acid-based fracturing fluids. Massive carbonates are often characterized by their extreme thickness anddepth, with accompanying high pressure and temperature. They often have extremelow permeability, and porosity. The permeability that is present is often inthe form of a fine interlacing of natural fractures and, in some cases, vugularsystems. Very little, if any, true matrix permeability exists. These primarycharacteristics have led to the difficulty in efficient, and effectivetreatment for stimulation. The thickness of these formations may range as high as several hundred feet, with depths of up to 25,000 feet. Thus, the low porosity dictates that theentire vertical extent of the formation must produce if ultimate recovery is tobe commercially attractive. Low permeability dictates that desired conductivitymust penetrate deeply into the reservoir to obtain commercial recoveryrates. THE PAPER WAS PRESENTED: at the 19th Annual Technical Meeting of The Petroleum Society of CIM, Calgary, May, 1968. Technology, January-March, 1969, Montreal Canada