Downhole instrumentation of the Khazzan tight gas appraisal wells provides a rare opportunity to quantify reservoir pressure and temperature dynamics. Several appraisal wells were tested initially for 3–4 weeks and subsequently shut in for approximately 1 year. The continuous downhole-gauge recordings of the resulting pressure buildups were then analyzed to quantify understanding of stimulation effectiveness, reservoir quality away from the wellbore, total producible connected gas, geomechanics, and wellbore hydraulics. This paper examines the pressure-transient analysis (PTA) of one representative well in the field.

Value of Permanent Downhole Gauges in Tight Gas

Dual permanent downhole gauges (PDHGs) were spaced approximately 100 m apart in the upper-­completion design, close to the perforations, to fulfill various surveillance requirements and provide the ability to measure gradients in the wellbore in real time. The completion could be tested with PDHGs and surface gauges. A considerable effort was made to ensure that the completions could withstand multiple high-pressure fracture-stimulation jobs. This included installing polished-bore packers and special-thickness tubulars. Preplanning of fracture designs using a variety of friction factors and likely fracture gradients was performed to narrow options and design the completions. Monobore completions were planned to enable running various plugs to isolate the pay intervals as required and to ease the running of logs, tools, and coiled tubing into the wellbore. The size of the completions was optimized for fracturing, not for fluid flow.