Objectives/Scope The Raageshwari Deep Gas Field in the western India, operated by Cairn India Limited, is a tight gas laminated reservoir (~0.1mD) with gross pay of ~700metres having numerous but small packets of good porosities and high gas saturations. This paper describes the holistic approach used to cover the maximum net pay of the laminated volcanic rock using the limited entry technique of fracturing with limited number of frac stages. It also summarizes how the conventional temperature logging practice post injection tests helped cover the net pay, improve and verify the limited entry technique, decide the number of frac stages and calibrate frac model. Brief discussion also includes the results of production logging used to access the reservoir response to stimulation. Methods, Procedures, Process The fracturing jobs were conducted through 3-1/2″ Monobore completion with target depths at ~3400m TVDSS. The challenge in developing a multilayered thick tight volcanic gas reservoir using the conventional single interval per stage perforating is that it would require more than 10 independent stages to effectively cover the available net pay which was deemed to be uneconomic. Limited entry Technique was used to combine number of sand packages in a single frac stage with high potential sands selected based on the reservoir and completion quality. Though fracturing simulators indicated theoretically that all of the perforation clusters which had different stresses and petro-physical properties, received pad and slurry to create a productive fracture, but verification was required. The effectiveness of the diversion was verified using a combination of Step rate/Step down tests, post mini frac/frac temperature surveys, post treatment pressure matching and time lapsed production logging. Results, Observations, Conclusions Limited Entry Technique has proved to be a cost effective method of increasing net pay coverage and EUR per well with minimum number of frac stages. Post SRT/mini frac/frac temperature surveys proved to be a very reliable, efficient and cost effective method for determining which perforations were taking fluid and the fracture heights which were generated. The heights obtained from the temperature surveys along with the pressure data/DFITs, were used to calibrate the hydraulic fracturing simulator. Also the production logging is showing the contribution form the all the targeted sands. Novel/Additive Information The application of limited entry technique, its verification using conventional temperature surveys and production loggings and the various operational and engineering learning acquired during planning to execution phase is an innovative and integrated approach in itself to exploit multilayered deep gas volcanic reservoir. Also pumping schedule modification like conducting step rate/down test in the pad sage or multiple step down tests in the same frac job were conducted while perforating individual interval/cluster

Hydraulic fracturing has evolved as the preferred completion strategy for low-permeability reservoirs in India. Hence, a hydraulic fracturing technique that maximizes production and is also operationally efficient will provide an optimum solution for the development of these reservoirs. A channel fracturing technique recently applied to more than 20 treatments for various operators in different fields and reservoirs in India has been delivering superior production results and has proved to be operationally more efficient compared to conventional hydraulic fracturing operations performed in India. Proppant is pumped in pulses at the surface during the channel fracturing technique. These pulses create stable channels within the hydraulic fractures thus decoupling fracture conductivity from the proppant pack itself which result in providing near-infinite fracture conductivity. An earth model was prepared from petrophysical measurements including acoustical data which allowed for the calculation of stresses that are required for hydraulic fracture modelling. These preliminary models were further calibrated based on pressure data gathered during fracture diagnostic tests and this calibrated model was used for the final treatment design. Post-treatment production evaluation was performed by applying nodal analysis and by comparing actual production with predicted production from a reservoir simulator. Treatment evaluation indicated higher fracture conductivity for channel fracturing technique than that of conventional treatments and this led to higher production. Fracturing fluid recovery has also been higher as compared to conventional treatments. Screenouts were eliminated on the treatments that applied the channel fracturing technique. This allowed fracturing zones that might not have been completed with conventional treatments. The amount of proppant pumped per stage has been reduced by nearly 50% as compared to conventional treatments and treating pressures in general have been lower which has led to lower horsepower consumption on the treatments. These successful hydraulic fracturing treatments have confirmed the applicability of the channel fracturing technique in the low-permeability reservoirs of India. This paper presents channel fracturing treatments that have been performed for the first time in India including treatments performed with heated fluid expanding the envelope for the technology application. This paper identifies a solution for screenouts during hydraulic fracturing treatments while maximizing production from low-permeability reservoirs.

Objectives/Scope The Raageshwari Deep Gas Field in the Western India, operated by Cairn, Oil and Gas vertical of Vedanta Limited, is a tight gas laminated reservoir with an average permeability of 0.1mD and a gross pay interval of ~700 metres. It is characterized by numerous packets of good porosity with high gas saturation. When the successful development of a reservoir is based on the ability to accurately model and install hydraulic fractures, verification of the fracturing models is critical. Verifying the fracture height is one way to reduce the uncertainty in the model results. This paper describes how the Pulsed Neutron Logging (PNL) was used to determine the fracture height in near vertical well by detection of boron, a primary constituent of borate based crosslinked fluid systems. The discussion will also include the benefits of quantifying the actual fracture height such as determination of the required number of stages and calibrating the fracturing simulator. Methods, Procedures, Process The PNT log was designed as an alternative to temperature and radioactive tracer logs and has been successfully used for the identification of channels in the cement sheath surrounding the casing, fluid movements, gas migrations etc. in both production and injection wells. PNL is used to track the movement of a saline solution of borax and water by measuring changes in the capture cross section of an interval caused by the injected borax. The above technique involves running a base PNL pass, injecting a boron solution into the interval, and then making the post injection PNL passes. The boron solution generates a significant change in logging tool response, enabling the tool to identify solution movement inside and outside the casing. The completion strategy in Raageshwari incorporates hydraulic fracturing through near vertical 3-1/2" monobore wells placed in 6" hole. Therefore, 8-10" depth of investigation of the PNL is sufficient to measure the frac height in the near wellbore area by measuring the boron present in the frac fluid in the fracture and the area adjacent to the fracture. Temperature logging was also performed in tandem with the PNL as an additional means of estimating fracture height. Results, Observations, Conclusions The pre-and post frac PNL survey responses were sufficiently different to enable estimation of the fracture height and the results were comparable to the heights obtained from the temperature logs. Knowing the fracture height provided an additional constraint which improved the fracture modeling. This technique is a cost effective way of determining fracture height without the need of pumping any additional hazardous (radioactive) or expensive materials. Its main advantage over temperature logging is its lower sensitivity to delays in the post fracture logging process. Novel/Additive Information The use of PNL for the fracture height determination from simple detection of boron present in the borate based cross linked fluid.

Cairn India Ltd & ONGC completed a joint venture appraisal of the Barmer Hill (BH) field in the Rajasthan block of India in 2015. The objective was to evaluate the effectiveness of horizontal multi-frac completions. The Barmer hill field is a moderate permeability (0.5 – 4 mD) oil bearing porcellanite with alternating sequences of tight shale. To produce this reservoir economically, hydraulic fracturing was the obvious choice of stimulation and was performed on a number of vertical wells (see Shaoul et al. 2007). To better evaluate the development strategy, completions using either transverse or longitudinal fracture treatments were successfully designed, executed, and evaluated. In the appraisal phase, four vertical and four horizontal wells were drilled to appraise the Barmer Hill reservoir in the Mangala field. Two of the horizontal wells were drilled along the maximum horizontal stress direction and completed with multiple hydraulic fracturing stages, which generated longitudinal fractures along the lateral wellbore. The fracture orientation with respect to the wellbore was confirmed with micro-seismic monitoring. This fracture treatment strategy provided the opportunity to decrease the number of frac stages and exhibited lower treating pressures as predicted by standard elastic rock mechanics theory. While the initial productivity of the transverse fractured wells was expected to be almost 2.5 times more than the longitudinally fractured well, it only produced about 40% more. In addition, the EUR of the longitudinally fractured well is almost the same as the transversely fractured well. Based on the generated fracture geometry, theoretically these longitudinally fractured horizontal wells may also provide better effective sweep efficiency when converted to a water injector from a field development concept.

An appraisal well in the KG Onshore Block (a joint venture of Cairn India Ltd and ONGC) has provided key engineering and operational learning's. The objective of this well was to appraise two separate low permeability reservoirs (~ 0.1md) which are ~4300m deep and falls under HPHT conditions. Due to their low permeability; hydraulic fracturing was necessary to verify the production potential of these reservoirs. To cater this, the discovery well was re-designed and sidetracked so that it could handle the expected fracturing loads. Hydraulic fractures (~387,000 lbs of Proppant); biggest in terms of proppant placed in any single stage in India, were executed and then the well was completed with slim-hole selective completion in challenging underbalanced conditions to test these reservoirs selectively. This paper primarily talks about the key constraints while planning and designing this well and then deals in detail on the learnings while executing this unique completion operation. Details on the fracturing design were already covered by Barasia et al. in SPE-171421-MS. The paper concludes with production results and the key reasons which led to ~7 fold increase with respect to previous appraisal well, as observed while production testing.