No abstract

No abstract

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 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

The evaluation of transmission zeros is of great importance for the control engineering applications. The structures equipped with piezoelectric patches are complex to model and usually require finite element approaches supplemented by model reduction. This study rigorously investigates the influence of mesh size, model reduction, boundary conditions (free and clamped), and sensor/actuator configuration (collocated and non-collocated) on the evaluation of transmission zeros of the piezoelectric structures. The numerical illustrations are presented for a thin rectangular plate equipped with a single pair of piezoelectric voltage sensor/ voltage actuator. Through the examples considered in this study, a link is presented between the static response (or static deflected shape) and the transmission zeros of the piezoelectric structures. This interesting observation forms the basis of: (i) a local mesh refinement strategy for computationally efficient estimation of the transmission zeros and (ii) a physical interpretation of the pole-zero pattern in the case of piezoelectric structures. The physical interpretation developed in this study helps in qualitatively explaining the pole-zero patterns observed for different configurations. It is also shown that this understanding of the relation between the static deformed shape and the transmission zeros can be used by the practitioners to modify the pole-zero pattern through a careful selection of the orientation and the size of the piezoelectric patches.