Acid Fractures Research Articles

Intravenous zoledronic acid reduced new clinical fractures and deaths in patients who had recent surgery for hip fracture

Source Citation Lyles KW, Colon-Emeric CS, Magaziner JS, et al. Zoledronic acid and clinical fractures and mortality after hip fracture. N Engl J Med. 2007;357:1799-809. 17878149

Zoledronic acid and clinical fractures and mortality after hip fracture

Het betreft een prospectieve gerandomiseerde dubbelblind placebogecontroleerde multicentrumstudie naar het effect van zoledroninezuur. Voor dit intraveneus toegediende bifosfonaat is een significante risicoreductie van fracturen aangetoond door intraveneuze toediening eenmaal per jaar bij postmenopauzale vrouwen.

Zoledronic Acid and Clinical Fractures and Mortality after Hip Fracture

Zoledronic Acid and Clinical Fractures and Mortality after Hip Fracture

Zoledronic Acid and Clinical Fractures and Mortality after Hip Fracture

Mortality is increased after a hip fracture, and strategies that improve outcomes are needed. In this randomized, double-blind, placebo-controlled trial, 1065 patients were assigned to receive yearly intravenous zoledronic acid (at a dose of 5 mg), and 1062 patients were assigned to receive placebo. The infusions were first administered within 90 days after surgical repair of a hip fracture. All patients (mean age, 74.5 years) received supplemental vitamin D and calcium. The median follow-up was 1.9 years. The primary end point was a new clinical fracture. The rates of any new clinical fracture were 8.6% in the zoledronic acid group and 13.9% in the placebo group, a 35% risk reduction with zoledronic acid (P=0.001); the respective rates of a new clinical vertebral fracture were 1.7% and 3.8% (P=0.02), and the respective rates of new nonvertebral fractures were 7.6% and 10.7% (P=0.03). In the safety analysis, 101 of 1054 patients in the zoledronic acid group (9.6%) and 141 of 1057 patients in the placebo group (13.3%) died, a reduction of 28% in deaths from any cause in the zoledronic acid group (P=0.01). The most frequent adverse events in patients receiving zoledronic acid were pyrexia, myalgia, and bone and musculoskeletal pain. No cases of osteonecrosis of the jaw were reported, and no adverse effects on the healing of fractures were noted. The rates of renal and cardiovascular adverse events, including atrial fibrillation and stroke, were similar in the two groups. An annual infusion of zoledronic acid within 90 days after repair of a low-trauma hip fracture was associated with a reduction in the rate of new clinical fractures and with improved survival. (ClinicalTrials.gov number, NCT00046254 [ClinicalTrials.gov].).

Deepwater Subsea Completion Benefits From Horizontal Fracture Stimulation

In late 2004, for the first time in history, a deepwater, subsea well was fracture stimulated using hydrajet-based fracturing with no downhole isolation. The well is located in 1,000 ft of water in the Campos Basin, southeast of Brazil. As the stimulated well had two branches abandoned due to drilling problems it behaved like a triple-lateral in terms of stimulation design. The 2.5-day treatment for Petrobras, closely monitored in real time from Duncan, Oklahoma, and Macaé and Rio, Brazil, resulted in five acid fractures created using the ZCA acid system. Production rate for the first 15 production days following the treatment with Halliburton’s SurgiFrac service approximately doubled the maximum historical rate of this well and was approximately four times the monthly production rate. As with vertical wells, in horizontal completions underachieving wells are common. This can be caused by many things, such as unexpectedly low permeabilities in the area; however, in horizontal wells, underperformance often is attributable to one or more of the following: - Permeability anisotropy (especially vertical-permeability limitations). - Skin damage or near-wellbore plugging of a natural-fracture network. - Ineffective stimulation techniques. The third item is especially the case in openhole horizontal wells and even more so in wells that are completed with slotted or preperforated liners. Perforated liners could be deemed the worst-case scenario when attempting to place multiple hydraulic fractures in the horizontal section. Controlling Fracture Placement This technology is the first method to resolve the problem of openhole fracture-placement control using dynamic diversion and consists of a combination of three processes—through-tubing hydrajetting, through-tubing hydraulic fracturing, and coinjection down the annulus with separate pumping equipment. An important aspect of this technique is dynamic sealing capability (Fig. 1). Unlike other techniques that require hardware-type packers or plugs or even chemical plugs, this process creates a seal using fluid movement. Packers are generally not used; therefore, the existence of passageways behind liner or through fractures rarely affects performance. The technique is based primarily on the Bernoulli principle, which states that the energy level of a fluid is generally maintained constant. To accomplish the SurgiFrac process, a jetting tool is placed near the toe of the well and is then used to jet perforate the casing and the formation rock, forming a 4- to 6-in.-deep cavity. Based upon the Bernoulli equation, as pressurized fluid exits the jet-ting tool, the pressure energy is transformed into kinetic energy or velocity. Since the fluid velocity around the jet stream is the highest, pressure in this area is the lowest (the fluid does not tend to “leak” out). Conversely, fluid from the other areas of the well will flow into the jetted area. The fluid contains some abrasives to help the fluid penetrate the steel liner and the formation rock. As cavities are formed by each jet, high-velocity fluid impacts the bottom of the cavity (i.e., velocity becomes zero—an energy change from kinetic back to potential energy, or pressure), causing pressure inside the rock to become high enough to create a fracture. Annulus pressure is then increased to assist in fracture extension. After the fracture is completed, the tool is moved to the next fracturing position and another fracture is placed.

New Model of Acid-Fracture Conductivity Based on Deformation of Surface Asperities

Summary Acid-fracture conductivity is affected by the aperture and contact area of the fracture under closure stress. This, in turn, depends on the surface asperities created by the acidizing process and the mechanical strength of these asperities. Acid contact time, acid leakoff, rock mechanical properties, and formation heterogeneity all affect the creation of hydraulic conductivity of an acid fracture. We have conducted a systematic experimental study to investigate the mechanisms of the creation of hydraulic conductivity in acid fractures, including characterization of the surface roughness created by acid etching, investigation of the damage to the rock compressive strength by acid, and measurement of hydraulic conductivity under closure stress. Experimental data show that longer acid contact results in rougher fracture surfaces and, in turn, higher hydraulic conductivity. However, acidizing also reduces the rock compressive strength causing the surface asperities to easily deform under stress. Based on our experimental results, a new fracture deformation model was derived which considers both the surface roughness and the rock mechanical properties. The fracture closure under stress is modeled as plastic deformation of asperities. Finally, a cubic law is used to calculate the fracture conductivity. The prediction of acid-fracture conductivity using this model with appropriate parameters shows good agreement with the experimental data.

Design and Installation of a Cost-Effective Completion System for Horizontal Chalk Wells Where Multiple Zones Require Acid Stimulation

Summary An innovative completion design that allows multiple acid fractures to be performed in horizontal subsea chalk formation wells with a single trip into the wellbore has recently been codeveloped by a major North Sea operator and an oilfield engineering/manufacturing/service company. The project was begun to develop a system that would allow multiple acid stimulations to be efficiently performed in the shortest possible time in the North Sea Joanne field. The system ultimately developed allows acid stimulation of up to 10 different zones in a single trip with no through-tubing intervention. The first well in which this new technique was used had seven zones, and three additional wells with 10 zones each were later completed. This paper presents the development of this system and case histories of the first four subsea wells requiring stimulation. The key element of the system is a multistage acid fracture (MSAF) tool that is similar to a sliding sleeve circulating device and is run in the closed position. Up to nine MSAF tools can be run in the completion with isolation of each zone being achieved by hydraulic-set retrievable packers that are positioned on each side of an MSAF tool. Each sleeve contains a threaded ball seat with the smallest ball seat in the lowest sleeve and the largest ball seat in the highest sleeve. With this system, stimulation of 10 separate zones is accomplished in 12 to 18 hours. A unique procedure that lubricates various sized, low specific gravity (SG) balls into the tubing and, then, pumps them to a mating seat in the appropriate MSAF tool to seal off the stimulated zone is used. This allows stimulation of the next zone, which is made accessible by opening the sleeve. This technique provided a substantial reduction in the operation time normally required to stimulate multiple zones and allowed the stimulations to be precisely targeted within the reservoir. The case history data provides comparisons in operation times between traditional stimulations and this new method, as well as the significant enhancements to cost efficiency that resulted from its use. Additionally, this completion method allowed the stimulations to be designed and matched to the requirements of each reservoir zone, which provided the most cost-efficient treatments possible.

How To Engineer a Fracturing Treatment

There are many causes of abnormally low well production rates, and a good engineering approach should identify them. They include low permeability, low reservoir pressure, high bottomhole pressure (BHP), high reservoir fluid viscosity, and high skin. The remainder of this paper considers the elements that can contribute to a successful hydraulic-fracture-treating program. Not all the elements need to be done in every case. However, they should be considered carefully, because they might affect both the success and the interpretation of the fracture-stimulation treatment. Inadequate evaluation could fail to identify changes and improvements to include in subsequent treatments. The following sections cover the pretreatment, execution, and evaluation phases of hydraulic fracturing. As can be appreciated, the key phase in fracture design is the pretreatment analysis.

Trauma an acetylsalicylic acid-induced changes in hemostasis during liver resection in the rat.

The effect of acetylsalicylic acid and bilateral femoral crush fractures on hemostasis after liver resection was studied in the rat. Serum salicylate levels were dose-dependent and similar in traumatized and non-traumatized animals. Bleeding time was significantly shortened and blood loss significantly decreased after bilateral femoral crush fractures. Both these values were significantly increased in salicylate pretreated animals compared to controls. Combination of bilateral femoral crush fractures and administration of 0.7 mg/100 g b.w. acetylsalicylic acid after bilateral femoral crush fractures increased blood loss significantly. Normal APT times indicated that the intrinsic coagulation system was not affected. ADP- and collagen-induced platelet aggregation was diminished in all animals as compared to controls.