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Background Dacryocystorhinostomy (DCR) is an operation that creates a lacrimal drainage pathway into the nasal cavity to facilitate drainage of the previously obstructed excreting system. Objective To compare effectiveness and complications of external and endoscopic DCR for treatment of primary acquired [nasolacrimal duct obstruction (NLDO)]. Patients and methods The present study included 60 patients (38 females and 22 males) aged between 18 and 50 years complaining of epiphora owing to NLDO. Patients were subdivided into two groups: group A included 30 (50%) eyes of 25 patients who were subjected to endoscopic DCR, and group B included 30 (50%) eyes of 27 patients who were subjected to external DCR. Results In this study, the right eye was more commonly affected than left eye. The percentage of right eye affection was 53.3% and left eye affection was 33.3%%. Massive intraoperative bleeding in group A was seen in five (16.5%) cases, whereas in group B, massive intraoperative bleeding was noted in nine (29.7%) cases. The difference was statistically nonsignificant (P=0.617). The successful surgical outcome after 6 months was achieved in 28 (92.4%) of 30 patients for the endoscopic DCR and 26 (85.4%) of 30 patients for external DCR surgery. The difference was not statistically significant (P=0.604). Conclusion DCR is the standard treatment for NLDO. It can be performed by external or endoscopic approach. Both these approaches have minimal complications and comparable surgical outcome. However, endoscopic DCR is a safe, minimally invasive effective day-care technique with good aesthetic results.

Among the various enhanced oil recovery (EOR) processes, CO 2 injection has been widely utilized for oil displacement in EOR. Unfortunately, gas injection suffers from gravity override and high mobility, which reduces the sweep efficiency and oil recovery. Foams can counter these problems by reducing gas mobility, which significantly increases the macroscopic sweep efficiency and results in higher recovery. Nevertheless, CO 2 is unable to generate foam or strong foam above its supercritical conditions (for CO 2 , 1100 psi at 31.1 °C), and most of the reservoirs exist at higher temperatures and pressure than CO 2 supercritical conditions. The formation of strong CO 2 foam becomes more difficult with an increase in pressure and temperature above its supercritical conditions and exacerbated CO 2 -foam properties. These difficulties can be overcome by replacing a portion of CO 2 with N 2 because a mixture of N 2 and CO 2 gases can generate foam or strong foam above CO 2 supercritical conditions. Although many researchers have investigated EOR by using CO 2 or N 2 foam separately, the performance of mixed CO 2 /N 2 foam on EOR has not been investigated. This study provides a solution to generate CO 2 foam above its supercritical conditions by replacing part of CO 2 with N 2 (mixed CO 2 /N 2 foam). The mixed foam not only generates strong foam above CO 2 supercritical conditions but also remarkably increases the oil recovery. This solution overcomes the difficulties associated with the formation of CO 2 foam at HPHT conditions enabling the use of the CO 2 -foam system for effective EOR and other applications of CO 2 foam such as conformance control.

Sulfates when present in the formation water would attack and deteriorate the cementitious system. In the quest to investigate the possibility of using geopolymer systems in oil-well cementing, the durability of geopolymer in various corrosive environments has been simulated. Lightweight geopolymer systems exhibit different microstructural and macroscopic properties compared to the conventional geopolymer systems whose durability under sulfate attack has been widely investigated. It is therefore important to study the resistance of lightweight geopolymer to sulfate attack. A ternary geopolymer was formulated at 13 ppg (1.56 g/cm3) by admixing metakaolin, ground granulated blast furnace slag (GGBFS), and silica fume in an alkaline solution composed of sodium silicate and 10 M sodium hydroxide solution in a mass ratio 1:3. The geopolymer specimen was cured in a water bath at 163 °F for 72 h and subsequently submerged in a 50 g/L sodium sulfate solution for up to 2 days. The effect of the sulfate solution on the strength and the mechanism of the sulfate attack was analyzed using analytical techniques, pH, and ion exchange measurements. The compressive strength of the specimen at 72 h, having a value of 802 psi decreased by 19.8% and 26.2% after day 1 and day 2 in the sodium sulfate solution, respectively. Investigation of the mechanism indicated that the loss in strength was not a result of the formation of deleterious phases but rather the leaching of Na ions from the geopolymer indicated by the rise in the pH and amount of Na ions in the sodium sulfate solution after the geopolymer was submerged in a sulfate solution. Lightweight geopolymer has a relatively loose microstructure that reduces its tendency to inhibit the transport of alkalis during sulfate attack, making the effect of the sulfate environment more pronounced.

Foam enhanced oil recovery (EOR) techniques commonly use N2 and CO2 gases. Previous studies have compared the foam generated by these two gases, and it has been found that CO2 becomes weaker and less stable at its supercritical conditions, reducing its effectiveness in creating stable foam. In contrast, N2 forms stronger foam at these conditions. Limited research has investigated the use of a CO2/N2 mixture foam in bulk media. It was found that adding N2 to CO2 has shown potential in producing more stable foam in oil-free porous media. This article reviews the advantages and disadvantages of CO2 foam and potential methods of improving its use in oil production. In addition, the performance of mixed CO2/N2 foam in crude oil-saturated sandstone cores was studied and compared to pure CO2 foam, with optimization of total injection rate, CO2/N2 ratio, and foam quality to achieve maximum oil recovery and stable foam. Results showed that the mixed foam gave a higher recovery than the CO2 foam. The addition of N2 to CO2 improved foam stability and enhanced oil recovery up to a 20 % by volume N2, but beyond this range, oil recovery was adversely affected. Increasing foam quality up to 80% produced a finer-textured foam, improving stability and recovery, but beyond 90%, the foam becomes coarser and less stable, likely due to the formation of dry foam. Increasing the injection rate affected stability of foam and recovery of oil, as higher rates of injection produced high shearing rates that may cause collapse of foam. The study suggested useful outcomes for addressing supercritical CO2 foam instability in sandstone reservoirs and advancing understanding in the developing area of foam behavior research.