Enhanced Oil Recovery Pdf
Christian Swindler
Crude oil development and production in U.S. oil reservoirs can include up to three distinct phases: primary, secondary, and tertiary (or enhanced) recovery. During primary recovery, the natural pressure of the reservoir or gravity drive oil into the wellbore, combined with artificial lift techniques (such as pumps) which bring the oil to the surface. But only about 10 percent of a reservoir's original oil in place is typically produced during primary recovery. Secondary recovery techniques extend a field's productive life generally by injecting water or gas to displace oil and drive it to a production wellbore, resulting in the recovery of 20 to 40 percent of the original oil in place.
However, with much of the easy-to-produce oil already recovered from U.S. oil fields, producers have attempted several tertiary, or enhanced oil recovery (EOR), techniques that offer prospects for ultimately producing 30 to 60 percent, or more, of the reservoir's original oil in place. Three major categories of EOR have been found to be commercially successful to varying degrees:
The EOR technique that is attracting the most new market interest is CO2-EOR. First tried in 1972 in Scurry County, Texas, CO2 injection has been used successfully throughout the Permian Basin of West Texas and eastern New Mexico, and is now being pursued to a limited extent in Kansas, Mississippi, Wyoming, Oklahoma, Colorado, Utah, Montana, Alaska, and Pennsylvania.
Until recently, most of the CO2 used for EOR has come from naturally-occurring reservoirs. But new technologies are being developed to produce CO2 from industrial applications such as natural gas processing, fertilizer, ethanol, and hydrogen plants in locations where naturally occurring reservoirs are not available. One demonstration at the Dakota Gasification Company's plant in Beulah, North Dakota is producing CO2 and delivering it by a 204-mile pipeline to the Weyburn oil field in Saskatchewan, Canada. Encana, the field's operator, is injecting the CO2 to extend the field's productive life, hoping to add another 25 years and as much as 130 million barrels of oil that might otherwise have been abandoned.
In September 2010, DOE competitively selected seven Next Generation CO2 EOR research projects. Four projects are developing techniques for mobility control of the injected CO2. Novel foams and gels have the potential to prevent the highly-mobile CO2 from channeling through high-permeability areas of a reservoir, leaving un-swept, unproductive areas of the reservoir. The four projects are:
Enhanced recovery after major surgery (ERAS) protocols are evidence-based, multimodal approaches used to facilitate recovery after major surgical procedures in the preoperative, intraoperative, and postoperative periods. Anesthesia management plays a key role in providing standardized care achieving earlier recovery. This activity reviews the role of the anesthesia team in improving recovery and care of patients after major surgical procedures such as major gastrointestinal surgery, urological surgery, gynecological surgery, thoracic surgery, orthopedic surgery, breast surgery.
Objectives:
- Summarize current literature covering the ERAS protocol.Review the multifactorial approach of ERAS protocols in the perioperative period.Identify the role of the anesthesiologist in the ERAS pathways.Explain the benefits and challenges of the implementation of the ERAS system.
ERAS pathways were first implemented at the start of the 21st century. For the past two decades, ERAS protocols have successfully improved perioperative mortality, morbidity, reduced length of hospital stay, decreased complications, and expedited recovery after major surgeries. This protocol is a multimodal approach that was instituted to enhance recovery postoperatively. These pathways are evidence-based guidelines applied at every stage of the perioperative period, including the preoperative, intraoperative, postoperative, and rehabilitation periods. ERAS protocols were initially implemented with colorectal surgeries and have since expanded to most major surgical procedures.[1] These protocols have been studied and carried out in various areas such as colorectal, thoracic, cardiac, urologic surgery, spine, neurosurgery, vascular, orthopedic, pancreatic, gynecological, and breast surgery.
ERAS protocols have been shown to alter physiological and psychological responses to surgery. The basis of implementing ERAS pathways resides in the maintenance of patients' preoperative physiologic and psychologic response by reducing the stress response throughout the perioperative period.[2] While surgeries may differ in their requirements and their impact on the patient, ERAS protocol is a structured, multimodal, multidisciplinary, fast-track approach that provides evidence-based standardized management to patients undergoing different types of surgeries.[3]
Coordination is required between members of the perioperative period to ensure successful implementation of ERAS protocols, including the surgical team, anesthesia team, nursing staff, preoperative, intraoperative, and postoperative personnel. The anesthesiologist is a key member of this team, optimizing the patient in the preoperative period, monitoring the patient in the intraoperative period to ensure hemodynamic stability, adequate depth of anesthesia, and analgesia, and ensuring optimal postoperative care. The anesthesiologist plays the most critical role in managing ERAS pathways, serving as the bridge between the preoperative, intraoperative, and postoperative periods.
ERAS pathways are evidence-based approaches critical to providing safe care and improving patient mortality, morbidity, and satisfaction in the perioperative period. These interventions optimize care in the perioperative period. Components of ERAS pathways can be subdivided into the preoperative, intraoperative, and postoperative periods.
The preoperative period allows medical personnel to evaluate the patient to determine whether or not the patient is stable enough for surgery, the type of surgery, the type of anesthetic, and the anticipation of postoperative location.[4] This period consists of interventions such as providing preoperative education, following preoperative fasting guidelines, eliminating bowel preps, providing routine antiemetic, venous thromboembolism, and antimicrobial prophylaxis. Preoperative education to patients and patient's families to set realistic expectations regarding their surgical and anesthetic experiences and postoperative pain relief. In addition, it also includes encouraging the patient to accelerate their progress postoperatively, including mobilization, i.e., early ambulation to prevent deep venous thrombosis, using incentive spirometry to improve postoperative atelectasis, thereby preventing pneumonia, and encouraging early oral intake.[5]
A big part of preoperative management also includes optimizing the patient before surgery, including managing their comorbidities, i.e., diabetes mellitus, hypertension, CAD, anemia, COPD, etc. Patients are also educated regarding their smoking use and alcohol consumption. ERAS protocols also focus on various strategies to optimize the patient, including providing education about sleep hygiene, relaxation strategies to reduce anxiety, and dietary modifications.[6] While patients are required to be NPO (nil per os) typically 8 hours before surgery, it has been suggested that maintaining hydration during the fasting period and minimizing the duration of the fasting period by continuing clear liquid until 2 hours before the procedure. Allowing carbohydrate loading via intake of a clear carbohydrate drink two hours before surgery helps the patient to remain close to their normal physiologic state. Carbohydrate loading has been shown to expedite the return of bowel function, reduce insulin resistance, maintain lean body mass and muscle strength, in addition to decreasing patient discomfort and anxiety.[7] The principle behind carbohydrate loading resides in the fact that this intervention prevents the body from entering a catabolic state which results from preoperative fasting.
Intraoperative ERAS protocols include providing multimodal non-opioid analgesics and antiemetics, incorporating regional anesthesia, antibiotic prophylaxis, normothermia, lung-protective mechanical ventilation, euvolemia, and minimizing drains and tubes such as early removal of foley catheters, surgical drains, and nasogastric tubes. Integration of prevention of surgical site infections and thromboembolic prophylaxis measures are already instituted at many hospitals across the country and have been incorporated into ERAS protocols. Preventative measures of surgical site infections include the use of chlorhexidine alcohol skin wipes, glove/instrument change with antibiotic irrigation before closure, intravenous antibiotics before incision, and providing antibiotics with bowel prep.[8]
Anesthetic management in the perioperative period plays a critical role in the ERAS system implementation. By facilitating the implementation of these protocols through communication and collaboration between personnel in the different perioperative periods, the anesthesiology team significantly improves patient satisfaction with their smooth transition from the preoperative to intraoperative to the postoperative period. In addition, the anesthesia team can profoundly impact patients' recovery postoperatively by choosing shorter-acting premedications and using reduced levels of volatile anesthetics, or using total intravenous anesthesia (TIVA), minimizing the use of opioids and adequate pain management, maintaining euvolemia, normothermia, and administering prophylactic antiemetics.
PONV is one of the most significant incapacitating factors concerning anesthesia. PONV is a common reason for a prolonged length of hospital stay as well as patient dissatisfaction. The administration of prophylactic antibiotics during preoperative and intraoperative periods was found to be very effective against PONV. Certain risk factors include younger age, female gender, prior history of postoperative nausea and vomiting, non-smokers, and history of motion sickness.[9] The anesthesia team can identify the factors and use measures to reduce nausea and vomiting. The use of a multimodal approach, prophylactic use of combination antiemetic therapy, including preoperative use of dimenhydrinate and intraoperative use of dexamethasone, ondansetron, and propofol can be very effective. A transdermal scopolamine patch is recommended for patients with a high risk for PONV. Intraoperative measures include minimizing volatile anesthetics, avoiding nitrous oxide, minimizing opioids, and maintaining euvolemia, which was found to be effective against PONV.
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