An increase in the number of explorations of deeper and hotter formations has prompted the need for an ultrahigh- temperature fracturing fluid. Conventional fracturing fluids are typically based on polysaccharides or their derivatives, which can provide enough viscosity to carry proppant deep into the formation at temperatures only up to 177 °C (350 °F). Beyond this temperature, these biopolymers hydrolyze too rapidly to be an effective and cost-efficient carry fluid; therefore, a new fluid was needed. We developed a new fluid system that can deliver the required rheological properties for successful fracturing operations up to bottom hole static temperature of 232 °C (450 °F) without the need for cool-down. This fluid is composed of a fast-hydrating synthetic copolymer and a metal crosslinker. This system has been engineered to provide a controllable crosslink mechanism and viscosity reduction profile to accommodate varying well conditions and job designs. Numerous proppant-pack conductivity tests have shown that this resilient fluid system can be broken and easily cleaned up at temperatures above 149 °C (300 °F). The rheological performance of the fluid, along with its high proppant pack regained permeability, makes the new fluid ideal in ultrahigh-temperature explorations. The fluid has already been successfully applied in the field. Preliminary lab and field implementation results are discussed.

The ultra-high pressure and temperature (HPHT) lower Cretaceous sand-shale layer in Krishna-Godavari basin (KG basin) (Fig. 1), in eastern India offshore shallow water, in the Godavari River interdeltaic region, is currently the world's highest-temperature petroleum reservoir being explored in the marine environment. It is a part of the fluvial sedimentary KG basin, which is recognized as holding India's largest gas reserves. Its area is approximately 50,000 km 2 and it extends from land to the shelf-slope and adjacent deep-sea area along the eastern passive continental margin of India. The bottomhole static temperature of the reservoir ranges from 350 to 450°F at 16,000 to 18,000 ft true vertical depth (TVD), with pore pressure gradient up to 0.85 psi/ft. The hydraulic propped fracturing technique is integral to the completion and well testing program in this typical tight reservoir.The design and delivery of hydraulic propped fracturing in such a complex reservoir and operational environment requires advanced technologies and meticulous planning and execution, including reservoir and geomechanical characterization derived from latest HPHT formation evaluation logging tools, implementation of integrated production simulation and fracturing modeling software, and application of ultra-HT completion and fracturing products. In addition to technical complexity, the limited drilling unit capability also required equipment planning that involved an integrated fracturing and testing wellheadstring-packer system, a project-specific modular HPHT stimulation boat and post-fracture flowback testing plan and equipment that included surface well testing and a coiled tubing nitrogen fleet.Several successful hydraulic fracturing operations were performed in this tight ultra-HPHT reservoir for multiple operators. This paper will describe the case history of the hydraulic fracturing completion campaign for one operator in the basin, in particular describing ultra-HPHT techniques and products that were key to the project delivery:• Basin modeling, reservoir, and geomechanical characterization workflow as an integral part of hydraulic fracturing design in complex frontier reservoir • Installation and preparation of modular HP/HT stimulation vessel custom built for this project • Implementation of synthetic fracturing fluids developed specifically for ultra-HT application up to 450°F in a high-pressure and high-shear environment.

Cambay is one of the oldest basins in India producing hydrocarbons since 1960's. It stretches almost 400 kilometers from south of Rajasthan to south of Gujarat in the western part of India and covering 53,000 sq. Km of total area. Cambay basin is contributing almost one-third of India's total onshore oil production. Raising production from Cambay basin is a considerable challenge as major producing fields are all Brownfield's. Hydraulic Fracturing (HF) is in use since 1980's to stimulate and enhance production from average to poor quality sands of Cambay basin. HF leads to better production results and has helped in enhancing production from this region for a long time. HF success ratio in stimulating these reservoirs dwindled significantly in the last decade due to continuous exploitation and decrease in saturation and reservoir pressures in the area. Enhancing fracture effectiveness & conductivity and reducing pressure drop within fracture was key to overcome this challenge and take the production to the next level. Maximizing conductivity of proppant pack has its own inherent limitations and this led to the application of channel fracturing for the first time in India in the Cambay basin. Channel fracturing results in decoupling fracture conductivity from proppant pack conductivity and results in infinite fracture conductivity, longer effective fracture half-lengths & reduction in pressure drop in the fracture. Creating stable fracture channels is highly dependent on rock mechanical properties and first hand evaluation of this decides applicability of this technology in a particular field/sand. This paper discusses the production results of wells treated with open channel fracturing compared to production results of offset wells stimulated by Conventional fracturing technology. Then it sheds light on basic requirement and key factors to be able to decide applicability of this technology in a particular field/sand. In the end applicability of this novel technology in all the major fields of Cambay basin will be discussed with the overall scope of redevelopment of all the major brown-fields of India.

The main basin at East coast of India, Krishna-Godavari (KG) Basin, is spread across more than 70,000 sq km. on land, shallow and deep water and holds India's highest gas reserve. Deen Dayan East (DDE) field is part of KG Basin in which lay deep HPHT tight gas reservoir that with current drilling and completion technologies can be made viable. An offshore appraisal well was directionally drilled down in Sshaped to the depth of 18700 ft MD to appraise the hydrocarbon potential of Lower Cretaceous Early Rift Fill sequences which was encountered in one of the offset wells in the same field DDE Block.Due to typical extremely tight nature of sandstone reservoir on deep gas well, hydraulic fracturing is the primary method and become inseparable technique to complete this well. Given its HPHT nature, with BHT up to 415F and in-situ stress up to 16000 psi, also the complexity of hydraulic fracturing on limited space of Jack-up rig, the hydraulic propped fracturing project become extremely challenging, both technically and operationally. In addition the limited flexibility on logistic due to short drilling time constraint, made some available fracturing HPHT technology not an option for this project, and require creative domestic solution. There were 2 independent reservoir layer were hydraulically fractured till the end of the well project, and significant gas were tested on post fracture completion from none prior to fracture. This paper illustrates the meticulous planning and preparation to design and execute the hydraulic propped fracturing for well testing appraisal purpose, as collaboration works from operator, fracturing services provider and other third party involved. The core objective of this paper is to capture all lesson learnt during this project delivery, review project operational and technical aspects, and summarize the recommendation and applicable techniques for the similar offshore HPHT hydraulic fracturing project in the future.-