Among the various neurotransmitter systems implicated in the mechanism of action of ascorbic acid (vitamin C), the relationship between the dopaminergic system and ascorbic acid is not particularly clear. Ascorbic acid is speculated to have an antagonistic effect on dopaminergic modulation. With this background in mind, in the present study we have seen the effect of ascorbic acid per se and in combination with typical and atypical antipsychotic agents against apomorphine-induced stereotypic behavior in mice. Male Laka mice weighing 20–25 g were used in the present study. Apomorphine-induced stereotypic behavior was used as an animal model. Various dopaminergic modulators were used. Ascorbic acid dose-dependently inhibited stereotypic behavior produced by apomorphine in mice. It potentiated the antipsychotic activity of haloperidol (0.1 mg/kg i.p.), a typical antipsychotic agent. When administered along with atypical antipsychotics, clozapine (1–2 mg/kg i.p.), sulpiride (10–20 mg/kg i.p.) and risperidone (0.0025 mg/kg i.p.), ascorbic acid also potentiated their activity. Also when given along with SCH-23390, a selective D₁ antagonist, an additive effect was observed. Ascorbic acid also inhibited the supersensitization response of apomorphine on reserpinization (2 mg/kg i.p.). Interestingly, at a lower dose (100 mg/kg i.p.), ascorbic acid potentiated the dopaminergic activity of apomorphine (0.5 mg/kg) and BHT-920 (0.25 mg/kg i.p.). However, when given concomitantly with SKF-38393, it failed to alter the response of SKF-38393. The data substantiate the hypothesis that ascorbic acid potentiated the activity of typical as well as atypical antipsychotics and that the effect of ascorbic acid on the dopaminergic system is markedly dose dependent; a low dose (100 mg/kg i.p.) potentiated the dopaminergic action while higher doses (400–1,600 mg/kg i.p.) blocked it.

There is increased confidence in LWD data because of the availability of new technology. Acquiring the maximum amount of data during drilling is standard practice when drilling highly deviated or horizontal wells to counteract high rig operating costs. In some cases, LWD services are completely replacing wireline services. Until just a few years ago, the wireline formation tester was the most common service used for formation pressure testing. Today, because of well complexity, the use of wireline testers is limited. High risks of tool sticking, invasion effects and additional rig days are some of the important factors giving LWD formation pressure testers a leading edge over its wireline counterpart. Baker Hughes' formation pressure testing-while-drilling tool, TesTrakTM, was deployed for ONGC, India in March 2014 as a part of the new LWD contract. The LWD formation testing tool was used in more than 50 wells, displaying exemplary performance with a sealing efficiency of more than 95%. Equipped with state-of-the art-technology, the LWD formation pressure testing tool saved a huge amount of rig time. The tool delivers real-time answers for wellbore connectivity, pressure depletion, reservoir compartmentalization, fluid identification and drainage. In addition to reservoir characterization, the tool also aided perforation decisions. The Mumbai High field comprises of two blocks: Mumbai High North (MHN) and Mumbai High South (MHS). The blocks are divided by a shale barrier that is used to assist in independent exploitation of reserves at the north and south fields of Mumbai High. Various oil and gas reservoirs, namely, (from top to bottom), L-I, L-II, L-III, L-IV and L-V, basal clastics and fractured basement are present on the Mumbai High project field. L-II and LIII are primarily the limestone oil reservoirs of Miocene age, and are further classified into several layers. [S.K. Mitra et.al., ONGC, Increased Oil Recovery From Mumbai High Through ESP Campaign; Offshore Technology Conference and Kharak Singh et.al. Mumbai High Redevelopment – Geo-Scientific Challenges and Technological Opportunities; 5th Conference & Exposition on Petroleum Geophysics][5,6,7] The FPWD service was run extensively in the Panna-Bassein-Heera block as well. This block located east of Mumbai High/Platform and south of Surat Depression has three distinct north-south to northwest-southeast trending tectonic units which lose their identity in Miocene. The western block is a composite high block dissected by a number of small grabens. The Central graben is a syn-sedimentary sink during Paleogene and Early Neogene. The eastern block is a gentle eastward rising homocline. The target zone is Bassein and all the drain holes in the field are drilled and completed in this zone. (From the information available on dgh official website)[8] Pressure tests are often recorded in the Bassein and Mukta formations. While testing in high-mobility formations, the tests were completed in a shorter time because of the controlled drawdown rate maintained by the tool. But, against tight, supercharged or low-mobility formations, it took more time to obtain stabilized pressure readings. Rugose hole conditions and dynamic mud losses, often observed in this field, made pressure testing even more challenging. To optimize testing in such formations, a detailed data set encompassing the testing parameters for the tool, formation type and other important observations was compiled after every job performed. With meticulous pre-job planning and real-time log analysis, test points were chosen in each zone to be tested. A detailed study of the data set aided in the selection of the test type and selection of parameters while testing in the same zone or zones with a similar log response. The lessons learnt from the previous formation pressure testing experience, coupled with efficient real- time monitoring from the base and good communication with the rig team and base team during the job, enabled testing time to be reduced significantly, thus saving rig time and simultaneously giving the data before the BHA is pulled out of hole. This paper presents the lessons learnt from the LWD formation pressure testing experience in India, the results obtained from various jobs, the accuracy of the data, the readings across various layers in Mumbai Offshore Basin (Mumbai High North and South and Neelam- Heera) and suggests best practices developed for the selection of optimized test parameters to increase accuracy, reduce testing time and reduce rig time without compromising data quality.

In a recent study, it has been demonstrated that ascorbic acid possessed antidopaminergic activity and modulate the glutamatergic neurotransmission in mice. With this background, the present study was undertaken to study the effect of ascorbic acid on the development of tolerance and dependence to opiate and its mechanism of action. Male Swiss mice weighing 20-25 g were used in the present study. Mice were made physically dependent on opioid by the chronic administration of morphine (10 mg/kg, twice a day, for 9 days) intraperitoneally. Ascorbic acid, haloperidol (dopamine antagonist) or MK 801 (NMDA receptor antagonist) was administered daily for 9 d before challenging the animals with morphine. The development of tolerance was assessed by noting the tail-flick latency on day 1, 3, 9 and 10. On the 10th day after the measurement of tail-flick latency, animals were challenged with naloxone (2 mg/kg., i.p.) and incidence of escape jumps were recorded by placing the animals in 45 cm high plexiglass container. Ascorbic acid (400-1600 mg/kg) dose dependently inhibited development of tolerance and dependence to morphine as noted from tail-flick latency. When given along with MK 801 (0.01 mg/kg., i.p) or haloperidol (0.1 mg/kg i.p.), ascorbic acid (800 mg/kg., i.p.) potentiated the response of MK 801 or haloperidol. In conclusion, it is hypothesized that inhibition of development of tolerance and dependence to morphine by ascorbic acid appears to have two components, namely dopaminergic and glutamatergic.

A number of exploratory wells were drilled in Eastern Offshore of India, encountering thick turbiditic sequences. The formation evaluation through conventional logging tools is a challenge in such depositional environments as the tools are unable to resolve thin beds and provides a weighted average log response over a collection of beds. In such environments, often the potential pay intervals are overlooked if comprehensive petrophysical analysis is not carried out. While the thin bed problem underestimates the reservoir potential, the orientation of measurement of the petrophysical properties further complicates the problem due to formation anisotropy. Another important characteristic of layered thin bed sand shale sequence is the acoustic anisotropy due to the transversely isotropic nature of sedimentary deposition. The multicomponent induction tool was logged in the study area, providing a tensor measurement of the horizontal (Rh) and vertical (Rv) components of resistivity. The well encountered thick turbidite sequence of laminated pay sands with very low resistivity contrast. The initial stochastic petrophysical analysis from conventional open hole log responses indicated poor reservoir quality with high water saturation. Integration of high-resolution acoustic data and VTI analysis with multicomponent induction tool shows a clear evidence of alternating shale and sand sequences in the target reservoir. A high-resolution processed acoustic porosity was incorporated to build the lithology model with multicomponent resistivity data. Integration of ResH, ResV and VTI into a Thomas-Stieber petrophysical model indicates potential hydrocarbon bearing sands at two depths which were further included to optimise the formation testing and sampling plan. During fluid sampling at the two identified depths, 54 and 157 ltrs. of fluid volume was pumped out before collecting samples by utilizing real time downhole fluid identification technologies. Optical absorbance and refractive indices were used to differentiate between miscible fluids. Clean-up from SOBM to formation oil was monitored using trends in representative channels of constantly changing absorbance spectrum. The formation testing results, therefore, were in good agreement with the identified pay intervals from the T-S model. Furthermore, Stoneley permeability analysis were carried out in the study area and calibrated with formation testing results. In the absence of imager data in the example well, formation dip was computed based on the multicomponent induction tool, which provided a close match to the OBM imagers, which struggled due to low formation resistivity, logged in adjacent wells. This paper highlights the integrated workflow of multicomponent resistivity data based Thomas Stieber petrophysical model with high resolution acoustic and formation tester results of the example well and its success in delineation of pay sand intervals.

Drilling through the thick shale sequence (Oligocene to Paleocene age) of Cauvery offshore showed severe wellbore instability in the past due to incompatible mud program that increased overall operational cost. While new high-angle sidetrack development wells had been planned, three major challenges need to be addressed. First, proper mud weight recommendation for preventing mechanical instability; second, introduction of a cost-effective mud system preventing time-sensitive failure; and finally, mitigating the environmental impact factor of the mud system. Geomechanical modelling and Hole Stability analysis had been performed based on available dataset. An optimized mud weight (MW) program was developed based on the analysis. Considering the time-dependent failure characteristics of the shale and overall cost effectiveness, just modifying the mud weight does not address all of the challenges delineated above. Consequently, special "high-performance water-based mud system (HPWBM)" was designed instead of oil-based mud (OBM). This HPWBM was formulated based on the nature of shales encountered. While drilling, real-time geomechanics further facilitated controlled drilling conditions and optimized the mud program. The well-based geomechanical model indicated a hydrostatic pore pressure gradient in the region. The relative magnitude of three principle stresses showed a normal fault stress regime and maximum horizontal stress (SHmax) azimuth appeared to be nearly aligned to the N-S direction. Hole Stability analysis showed that a minimum of 12 ppg mud weight was required to drill the 8½" section. The sidetrack holes had a maximum inclination of 75 to 77 degrees. Different polymers and bridging agents were added to prepare the customized HPWBM in order to address shale instability and formation damage due to overbalance. Real-time monitoring during drilling operation utilized logging while drilling (LWD) log data, drilling parameters and mud logging data to promote smooth drilling operations. Through systematic planning and execution, the high-angle sidetrack holes had been drilled with zero non-productive time (NPT) in terms of well bore stability. More than 50% cost reduction was achieved on the mud system. An integrated solution that includes pre-drill geomechanics, HPWBM system design and real-time well monitoring helped to reduce the risks due to model uncertainties while drilling high angle wells through the thick shale section. This approach helped to reduce significant operational cost with an improved success rate.