Evaluation of the potential for gas leakage along wellbores in the St. Lawrence Lowlands basin,Quebec, Canada

Wellbore attributes (i.e., deviation, casings and plugging characteristics) for 85 wells in the St. Lawrence Lowlands basin of southern Quebec were compiled from drilling reports and abandonment programs to provide an overview of the abandoned well characteristics and to establish a diagnosis on the long-term reliability of the completion and abandonment practices carried out by the companies since the beginning of oil and gas exploration. Using these data, the conventional and unconventional wells were divided into four categories: (1) conventional wells drilled before 1950, (2) conventional wells drilled between 1950 and 1970, (3) conventional wells drilled after 1970 and shale gas wells (all drilled after 2000). Very little information was available for wells drilled before 1950. More information was available for the wells drilled from 1950 to 1970 which is considered a transition period between old and modern technology. Conventional and unconventional wells drilled after 1970 were generally well documented and their attributes corresponded to API standards. A decision tree, inspired from the methodology proposed by Watson and Bachu (SPE Drill Complet 24(1):115–126, 2009.  https://doi.org/10.2118/106817-PA), was then created to assess the potential of leakage of each of the conventional and unconventional wells using the compiled attributes. The factors defining the probability of well leakage were wellbore deviation, height of cement in casing annuli (partially or fully cemented), type of abandonment plugs (cement or mechanical plugs) and drilling date (before or after 1970). Among the 85 wells assessed by this tree, the probability of leakage was higher than 50% for 55 wells (65% of wells). Wellbore deviation and lack of information on the construction and abandonment methods were respectively the primary and secondary causes of high probability of leakage of these wells.     

Geothermal Characterization of the St. Lawrence Lowlands Sedimentary Basin,Québec,Canada

Defining temperature at depth to identify geothermal resources relies on the evaluation of the Earth heat flow based on equilibrium temperature measurements as well as thermal conductivity and heat generation rate assessment. Such high-quality geothermal data can be sparse over the region of interest. This is the case of the St. Lawrence Lowlands sedimentary basin covering 20,000 km² to the south of Québec, Canada, and enclosing only three wells up to a depth of 500 m with equilibrium heat flow measurements. However, more than 250 oil and gas exploration wells have been drilled in this area, providing for this study (parce que c'est 93 sinon) 81 locations with bottom-hole temperature up to a depth of 4300 m, however, not at equilibrium. Analyzing these data with respect to the deep geothermal resource potential of this sedimentary basin requires evaluating the thermal conductivity and heat generation rate of its geological units to properly extrapolate temperature downward. This was done by compiling literature and recent thermal conductivity measurements in outcrop and core samples as well as new heat generation rate estimates from spectral gamma ray logs to establish a first thermal assessment of geological units deep down into the basin. The mean thermal conductivity of the thermal units varies from 2.5 to 6.3 W/m·K, with peak values in the basal sandstones, while the heat generation rate varies from 1.6 to 0.3 µW/m³, decreasing from the upper caprocks toward the base of the sequence. After correcting the bottom-hole temperatures for drilling disturbance with the Harrison correction and subsequently for paleoclimate variations, results indicate a mean geothermal gradient of 23.1 °C/km, varying from 14 to 40 °C/km. Evaluating the basin thermal state from oil and gas data is a significant challenge facilitated by an understanding of its thermal properties.     

Selection effects in the SDSS quasar sample: the filter gap footprint

Locating the exact point of origin of the core radiation in active galactic nuclei (AGN) would represent important progress in our understanding of physical processes in the central engine of these objects. However, due to our inability to resolve the region containing both the central compact object and the jet base, this has so far been difficult. Here, using an analysis in which the lack of resolution does not play a significant role, we demonstrate that it may be impossible even in most radio loud sources for more than a small percentage of the core radiation at radio wavelengths to come from the jet base. We find for 3C279 that ∼85 percent of the core flux at 15 GHz must come from a separate, reasonably stable, region that is not part of the jet base, and that then likely radiates at least quasi-isotropically and is centered on the black hole. The long-term stability of this component also suggests that it may originate in a region that extends over many Schwarzschild radii.     

Evidence that the bursting component of the X-ray radiation from 3C 111 originates in the PC-scale jet

Evidence is presented indicating that the bursting component of the X-ray radiation detected in the nuclear region of the active radio galaxy 3C 111 comes from the blobs ejected in the pc-scale jet and not from the accretion disc. After each new outburst the radio flux density associated with it increases to a peak in ∼1 year and then subsides over a period of 1–2 years with the flux falling off exponentially as the blob moves outward and dissipates. Similar peaks (bursts) are seen in the X-ray light curve and a cross-correlation between the two shows a very high correlation with the X-ray peaks leading the radio peaks by ∼100 days. A second cross-correlation, this time between the radio event start times and the X-ray light curve, also shows a significant correlation. When this is taken together with the long (∼1 yr) delay between the start of each ejection event and its associated X-ray peak it indicates that this bursting component of the X-ray flux must be associated with the ejected blobs in the pc-scale jet and not with the accretion disc. Because X-ray telescopes do not have the resolution required to resolve the accretion disc area from the pc-scale jet, this paper is the first to present observational evidence that can pinpoint the point of origin of at least those long-timescale X-ray bursts with durations of 1–3 yrs.     

Variability in trap catches for an American lobster,Homarus americanus,spring fishery

At‐sea sampling is a common approach used by fisheries scientists to assess changes in fished populations. Traditional sampling programmes focus on short intensive sampling periods by fisheries personnel, although there has been a move to increase temporal sampling frequency within a fishing season by using harvesters. To determine the suitability of these two options, we compared the precision of estimates obtained for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. The sampling variance estimation for the mean catch‐per‐unit‐effort (CPUE) was based on a three‐stage sampling design with days as the primary unit, and buoy and trap as secondary and third stage units, respectively. Using the estimated variance components to predict and compare the variance of the mean CPUE for different at‐sea sampling designs, we show that it would be more efficient to sample a few traps (at least 3) every day for the entire fishing season than the traditional at‐sea sampling of the entire fishing gear twice or three times in a season by scientific personnel. Designing a harvester‐based at‐sea sampling programme could be an efficient approach for reducing costs while gathering essential fishery data, improving dialogue between the industry and scientists, and increasing harvesters’ participation in managing the resource.     

Silicon carbide clusters in circumstellar environment

The presence of small clusters of silicon carbide (SiC) in circumstellar dust shells surrounding late-type stars is inferred from a broad emission feature peaking at around 11 micrometre in infrared spectra (Little-Marenin ,1986 ApJ Lett. 307, L15). These clusters are expected to condense from molecular arrangements composed of a few carbon and silicium atoms which are present in stellar winds surrounding carbon-rich late-type stars. we have searched for all the possible geometric structures of SiC _n ⁺ radicals (n <= 5) with help of ab initio calculations (T = 0 K). Vibrational frequencies of the most stable species have then been determined . the destabilizing influence of a finite temperature effect on these structures has also been studied by using general considerations of thermal statistics. We show that for n >= 3 linear structures are energetically favored compared to the planar and three-dimensional ones. A comparison with other results published in this context is also made.     

Protecting window‐size female American lobster,Homarus americanus,to increase egg production

A new conservation measure aimed at protecting the larger broodstock (females with a carapace length between 115 and 129 mm, i.e., window‐size females, WSF) to enhance egg production was implemented in 2003 for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. To assess the effectiveness of this new measure, a tagging project was carried out between 2004 and 2007 in the Hillsborough Bay area with the collaboration of local harvesters. Based on a single mark‐recapture Petersen model, the estimated catch rates of WSF not carrying eggs under the abdomen in the study area varied between 40% and 53%. The catch‐per‐unit‐effort (animals per 100 traps) of both berried (egg‐bearing) and non‐berried WSF increased from 0.2 to 0.8 and 1.0 to 1.6, respectively, between 2004 and 2007. Based on the estimated number of non‐berried WSF in the population observed during the spring fishery between 2004 and 2007, the potential total egg production for WSF was estimated at 1.1 billion in the study area. From this total, 515 million eggs would have been produced by WSF directly protected by the conservation measure, i.e., females that would have been harvested if not for the new regulation. Finally, the contribution of berried WSF to the annual egg production in the study area increased from 4% to 23% between 2003 and 2007 based on the at‐sea sampling programme and the fecundity curve. WSF that represented 10% of the total berried female population in 2007 contributed 23% of the annual egg production. Hence, the protection of WSF seems to be an effective conservation measure to increase egg production based on the catch‐per‐unit‐effort and egg production.     

Message framing influences perceived climate change competence, engagement, and behavioral intentions

The effect of motivational versus sacrifice message framing on perceived climate change competence, engagement, and 15 mitigative behavioral intentions was examined in a large Canadian community sample (n = 1038). Perceived competence, engagement, and several behavioral intentions were significantly greater after exposure to motivational framing than after sacrifice framing. Gender, age, income, and educational level moderated some results, and moral engagement and agentic language also played a role. The results support the use of motivational frames rather than sacrifice frames to increase the climate-related engagement and activation of community members.