Integration Success Story in Shilaif Shale Oil from Vertical Pilot to Horizontal

The development of unconventional target in the Shilaif formation is in line with the Unconventional objective towards adding to ADNOC reserves. For future optimization of development plans, it is of utmost importance to understand and test and therefore prove the productivity of the future Unconventional Horizontal Oil wells. The Shilaif formation was deposited in a deeper water intrashelf basin with thicknesses varying from 600 to 800 ft from deep basin to slope respectively. The formation is subdivided into 3 main composite sequences each with separate source and clean tight carbonates. The well under consideration (Well A-V for the vertical pilot and Well A-H for the horizontal wellbore) was drilled on purpose in a deep synclinal area to access the best possible oil generation and maturity in these shale Oil plays. Due to the stacked nature of these thick high-quality reservoirs, a pilot well is drilled to perform reservoir characterization and test hydrocarbon type and potential from each bench. Fracturing and testing are performed in each reservoir layer for the primary purpose to evaluate and collect key fracturing and reservoir parameter required to calibrate petrophysical and geomechanical model, landing target optimization and ultimately for the design of the development plan of this stacked play. Frac height, reservoir fluid composition and deliverability, pore pressure are among key data collected. The landing point selected based on the comprehensive unconventional core analysis integrated with petrophysical and geomechanical outcomes using post vertical frac and test results. Well A-H was drilled as a sidetrack from the pilot hole Well A-V. This lateral section was logged with LWD Triple Combo while Resistivity Image was acquired on WL. Based on the logging data the well stayed in the target Layer / formation, cutting analysis data for XRD and TOC was integrated with the petrophysical results in A-H well. Production test results from subject were among the highest rate seen during exploration and appraisal of this unconventional oil plays and compete with the current commercial top tier analog unconventional oil plays. Achieving those results in such early exploration phases is huge milestone for ADNOC unconventional exploration journey in UAE and sign of promising future development.

Experimental Investigation of Hydrocarbon Gas Huff-N-Puff Injection into the Live-Oil Window of Eagle Ford

The hydrocarbon gas huff and puff (HnP) technique has been used to improve oil production in unconventional oil reservoirs where excess capacity of produced gas is available and hydrocarbon prices are in a range to result in an economically viable case. Eagle Ford (EF) is one of the largest unconventional oil plays in the United State where HnP has been applied for enhanced oil recovery (EOR) at reservoirs within various oil windows. Our previously published Huff-n-puff results on dead oil with produced gas from Eagle Ford (EF) showed the recovery factor of hydrocarbon varying from 40 to 58%. The objective of this paper is to extend the experiments to live oil with EF core plugs to investigate the mechanisms of HnP which are affected by the composition of injected gas and resident oil, injection and soaking time as well as injection/depletion pressure gradient. Eagle Ford live oil and natural gas produced from the target area were used for HnP tests. Four representative core plugs were used with the tests conducted at reservoir conditions (125 °C and 3,500 psi). The live oil experiments with four reservoir core plugs showed an improvement in oil recovery with recovery factor (RF) varying from 19.5 to 33 % in six cycles of HnP, whereas the primary depletion on the same core plug showed RF below 11 %. A lower recovery factor of HnP from live oil saturated core in this study was observed as compared to dead oil saturated core reported in a previous publication. It is attributed to a lesser diffusion effect on mass transfer between injected gas and resident oil when the core is saturated with live oil. This behavior is displayed by the pressure decline curve during the first soaking period. A sharper diffusion pressure decline occurred in the dead oil saturated core plug where a higher concentration gradient between injected gas and resident oil drives a faster gas transport into the oil due to the molecular diffusion during the soaking period.