Abstract
This paper presents the first new technology applications of reservoir fluid characterization and sampling while drilling in the United Arab Emirates. Four case histories provide details of this technology in the last two years, and the value added to the assets operating in different targeted reservoirs.
Cost and rig-time optimization demands has motivated operators to utilize the fluid analysis and sampling tool designed for LWD to reach formation targets before they have been exposed to long period of invasion. This technology provides pressure testing, real-time in-situ measurements of formation fluid properties and downhole capture and retrieval of fluid samples. The applications proved valuable in obtaining required formation data and reducing operational time, cost and associated risks.
Results of this technology in the UAE were evidenced in the following applications:
An offshore field had original formation water with high salinity that, over time, mixed with low salinity injection water which affects water saturation log interpretation. The objective was to collect representative water from the formation (either original formation water or injection water) and this was complicated by water-based mud filtrate with its own unique salinity. Samples from three depths were collected and confirmed by laboratory analysis to be representative formation water. The refractive index provided a clear way of discriminating the water-based mud filtrate from formation water.
A field with known condensate was scheduled for fluid sampling to check for injection gas break-through. LWD sampling was used because of the high mobility of the gas and condensate. Seven successful samples were collected and subsequent lab analysis confirmed condensate in the reservoir.
Pressure testing and sampling while drilling was performed in a heterogeneous carbonate reservoir. A valid oil gradient was detected after completing several good pressure tests in a short period after drilling. The formation fluid pump-out was initiated to identify and collect oil and water samples that helped in determining an accurate oil-water contact.
A fluid sampling operation was performed in a highly deviated offshore well to provide the asset an operational alternative to a complex pipe-conveyed wireline logging operation. The pump-out started shortly after drilling to limit invasion. Five samples were obtained and brought to surface to confirm the real time fluid identification. The case will discuss the challenges and complication of the operation in a highly deviated well crossing several reservoirs.
A review of the presented cases helps demonstrate LWD sampling technology as a successful method in the Middle East for characterizing downhole fluid, supporting real-time decision making, minimizing rig time, cost and associated operational risks.
