Water Drive Characteristic Curve Theory of Low Permeability Reservoir

The so-called water flooding characteristic curve refers to the oilfield water injection (or natural water drive) development process, a relationship between curve cumulative oil production, cumulative water production and accumulation of fluid production. These curves have been widely used for water injection development of dynamic and recoverable reserves forecast. After many years of practical application, summed up the four kinds of water drive characteristic curve, they have a good practical significance. Recoverable reserves are important indicators of field development and also the main basis for planning and design, while the application of water flooding characteristic curve can be predicted oil recoverable reserves. Four kinds of water flooding characteristics discussed above curve are mainly applied in high-permeability oil field, which did not consider starting pressure. In fact we should consider the impact of low permeability oilfield actuating pressure gradient on the water content. Here, we deduce the formulation considering the actuating pressure.Key words: Low permeability; Water flooding; Actuating pressur

Investigation on Actuating Pressure Gradient of Low Permeability Reservoir

Due to the presence of actuating pressure of low permeability reservoir, researching on actuating pressure gradient of low permeability reservoir is necessary. While actuating pressure gradient is relevant to permeability and porosity, it can be obtained through laboratory experiments, well testing interpretation method and theory derivation combined with practical application method. The results of a large number of laboratory experiments show that actuating pressure is related to permeability. The greater the permeability is, the smaller the actuating pressure is. They both present the similar hyperbolic relationship; the greater the viscosity of the oil is, the greater the actuating pressure is. Here, we get the actuating pressure gradient formula through the method of theory derivation combined with practical application, meanwhile we put forward the relationship between actuating pressure gradient and permeability, porosity and viscosity.Key words: Low permeability reservoir; Actuating pressure gradient; Porosity; Fluid viscosit

Effects of antenatal hypnosis on maternal salivary cortisol during childbirth and six weeks postpartum-A randomized controlled trial

BACKGROUND:Cortisol has been used to capture psychophysiological stress during childbirth and postpartum wellbeing. We explored the effect of a brief antenatal training course in self-hypnosis on salivary cortisol during childbirth and 6 weeks postpartum. METHODS:In a randomized, controlled trial conducted at Aarhus University Hospital Skejby Denmark during the period January 2010 until October 2010, a total of 349 healthy nulliparous women were included. They were randomly allocated to a hypnosis group (n = 136) receiving three one-hour lessons in self-hypnosis with additional audio-recordings, a relaxation group (n = 134) receiving three one-hour lessons in various relaxation methods with audio-recordings for additional training, and a usual care group (n = 79) receiving ordinary antenatal care only. Salivary cortisol samples were collected during childbirth (at the beginning of the pushing state, 30 minutes, and 2 hours after childbirth), and 6 weeks postpartum (at wake up, 30 minutes after wake up, and evening). Cortisol concentrations were compared using a linear mixed-effects model. Correlations between cortisol concentrations and length of birth, experienced pain and calmness during birth were examined by a Spearman rank correlation test. FINDINGS:During childbirth, week correlations were found between cortisol concentrations 30 minutes after childbirth and length of birth. In the beginning of the pushing state and 2 hours after childbirth, we found a tendency towards higher cortisol concentrations in the hypnosis group compared to the other two groups (hypnosis versus relaxation p = 0.02 and 0.03, hypnosis versus usual care p = 0.08 and 0.05). No differences were observed in cortisol concentrations between the groups 30 minutes after childbirth (hypnosis versus relaxation p = 0.08, hypnosis versus usual care 0.10) or 6 weeks postpartum (hypnosis versus relaxation: p = 0.85, 0.51, and 0.68, hypnosis versus usual care: p = 0.85, 0.93, and 0.96). CONCLUSION:Antenatal hypnosis training may increase the release of cortisol during childbirth with no long-term consequences. Further research is needed to help interpret these findings

Neonatal phototherapy and clinical characteristics : the Danish national patient registry 2000–2016

Purpose: Phototherapy is the standard treatment for neonatal hyperbilirubinemia. It is important to collect data on phototherapy to support research related to the efficacy and safety of phototherapy. We explored the registration of phototherapy in the Danish National Patient Registry (DNPR) and the clinical characteristics of neonates treated with phototherapy. Methods: We identified children born alive in Denmark from 1 January 2000 through 30 November 2016 from the DNPR (N=1,044,502). We calculated the proportion of children registered that received phototherapy during the neonatal period and examined temporal trends, both nationwide and at the level of individual hospitals. In a sub-cohort of children born at Aarhus University Hospital (AUH) in 2002–2016 (N=71,781), we analyzed the proportions of children registered that received phototherapy, according to sex, gestational age, birth weight, and neonatal characteristics, like Apgar score, birth asphyxia, and infections. Results: We identified 11,295 (1.1%) registered that received phototherapy. The proportions of children registered that received phototherapy differed among hospitals (range: 0 to 4.1%). Nationwide registration was low during the study period, but it increased to 1.8% in 2016. For the AUH sub-cohort the proportion of children registered with phototherapy averaged 4.4% (N=3182, range:3.9– 5.1%). The proportion of children registered with phototherapy was inversely correlated with gestational age and birth weight, and positively correlated with neonatal characteristics, including low Apgar score, birth asphyxia, and infections. Conclusion: Phototherapy was under-reported in the DNPR and the proportions of children registered that received phototherapy differed among hospitals. The non-compulsory policy for reporting treatment and care in hospitals to the DNPR might explain the variation. The most consistent reporting was observed among children born in an university hospital, where 4.4% of children registered that received phototherapy, and phototherapy was inversely associated with gestational age, birth weight, and positively associated with clinical characteristics like birth asphyxia, and infections

Parity, mode of birth, and long-term gynecological health: A follow-up study of parous and nonporous women in the Australian Longitudinal Study on Women's Health cohort

Background:Although gynecological health issues are common and cause considerable distress, little is known about their causes. We examined how birth history is associated with urinary incontinence (UI), severe period pain, heavy periods, and endometriosis. Methods:We studied 7700 women in the Australian Longitudinal Study on Women's Health with an average follow-up of 10.9 years after their last birth. Surveys every third year provided information about birth history and gynecological health. Logistic regression was used to estimate how parity, mode of birth, and vaginal tears were associated with gynecological health issues. Presented results are adjusted odds ratios (OR) with 95% confidence intervals. Results:UI was reported by 16%, heavy periods by 31%, severe period pain by 28%, and endometriosis by 4%. Compared with women with two children, nonparous women had less UI (OR 0.35 [0.26–0.47]) but tended to have more endometriosis (OR 1.70 [0.97–2.96]). Also, women with only one child had less UI (OR 0.77 [0.61–0.98]), but more severe period pain (OR 1.24 [1.01–1.51]). Women with 4+ children had more heavy periods (OR 1.42 [1.07–1.88]). Compared with women with vaginal birth(s) only, women with only cesarean sections or vaginal birth after cesarean section had less UI (ORs 0.44 [0.34–0.58] and 0.55 [0.40–0.76]), but more endometriosis (ORs 1.91 [1.16–3.16] and 2.31 [1.25–4.28]) and heavy periods (ORs 1.21 [1.00–1.46] and 1.35 [1.06–1.72]). Vaginal tear(s) did not increase UI after accounting for parity and birth mode. Conclusion:While women with vaginal childbirth(s) reported more urinary incontinence, they had less menstrual complaints and endometriosis.</p

An International Contrast of Rates of Placental Abruption : An Age-Period-Cohort Analysis

Background Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide in-sights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Methods Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 197808), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries. Results Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (P <0.01). Conclusions There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.Peer reviewe