Speaker at Oil, Gas and Petroleum Engineering 2022 - Soumya Chandan Panda
Oil & Natural Gas Corporation Ltd, India
Title : Unconventional Tight Gas Reservoirs - A Case Study From KG Basin Offshore, India

Abstract:

Tight gas refers to natural gas reservoirs locked in extraordinarily impermeable, hard rock, making the underground formation extremely ‘tight’. The tight reservoirs are characterized by low permeability, large pressure gradient across reservoir, often layered and complex, high transient decline rate and comingled production. Tight gas reservoirs require significant well stimulation hydraulic fracture treatment or the use of horizontal or multi-lateral wells to produce at economic rates. An unconventional reservoir is one that cannot be produced at economic flow rates or that does not produce economic volumes of oil and gas without assistance from massive stimulation treatments or special recovery processes and technologies, such as steam injection. Typical unconventional reservoirs are tight-gas sands, coal-bed methane, heavy oil, and gas shales unlike conventional reservoirs, which are small in volume but easy to develop, unconventional reservoirs are large in volume but difficult to develop. Two wells (X-1and X-2) were selected to be evaluated. The petrophysical evaluations of these wells have been performed using integration of petrophysical logs and cross plots.
Optimum exploration of tight sands depends upon its petrophysical evaluation and geological understanding. Well log interpretation is an additional tool to identify the environment of deposition and tightness of the reservoirs. Minerals have been identified by integrating cross-plots from logs of two wells and are validated with sedimentological core studies. The petrophysical cross plots can be used for parameter picking for clay parameters and identification of common mineral types. For this aim, some cross plots, thorium versus potassium were investigated in the wells X-1 & X-2. As can be seen from the lithology cross plots, among the areas allocated for the minerals, some points have been distributed in the areas of the Kaolinite, Chlorite and heavy minerals. 
With hostile down-hole environments, well depths exceeding 5000m, temperatures reaching 400 degF and pressures exceeding 12000 psi, FSWC-ULP Slim for HT version rated 500?F was used in well X-1 for formation pressure recording and fluid sampling. The low permeability sands were tested to an extreme drawdown of close to 8000 psi at the sand-face to sustain reservoir fluid flow with the help of the special extra high-pressure pumping system.
It is recommended to use the full suite of HPHT Logging While Drilling in Cretaceous Formation. 1D-MEM prior to drilling of any HPHT well to know the precise pore pressure profiling is mandatory. Proper coring is to be carried out and extensive laboratory studies are to be carried out including Geo-mechanical to prepare representative petro-physical interpretation models and providing valuable geo-mechanical inputs for HF designing.  Deep Shear Wave analysis is recommended to know the possible fractures and their extent. Prodcution of such reservoirs, multi zone completions, oriented perforating, massive hydraulic fracturing, and cased-hole logging methods are all required to maximize recovery and minimize the cost associated with well completions. 

Audience Take Away:

  • Tight gas reservoirs have a huge future potential for production. The Cretaceous formation of the Krishna-Godavari (KG) Basin in the East Coast of India comprises of sub-millidarcy Syn-rift sands with significant volumes of untapped hydrocarbon reserves.
  • Improvements in completion and drilling technology will allow well identified geologic traps to be fully exploited, and improvements in product price will allow smaller accumulations or lower-rate wells to exceed economic thresholds, but this is true in virtually every petroleum province.
  • Computation of saturation in low porosity reservoirs is prime challenge due to high resistivity developed either due to fluid nature or poor porosity development.Wells in high-pressure, high-temperature (HPHT) conditions are always categorized as high-risk and expensive, and formation evaluation in the well poses challenges.An enormous volume of unconventional oil and gas will be there to fill the gap once conventional oil begins to decline in the next 5 to 20 years.
     

Biography:

Soumya Chandan Panda studied Applied Geophysics at the Indian School Of Mines, India and graduated as MS in 2015. He then joined Oil & Natural Gas Corporation Ltd, India as a petrophysicist in 2015. He was responsible for Well-logging operations in the Offshore fields on the eastern coast of the India. He was promoted to Senior Petrophysicist in 2020 and he is Incharge of the Procurement and Contract Management group since then. He has presented in multiple International Conferences like EAGE Annual Conference 2015,2017,2019 and Geoscience-2020.

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