Newly-Developed Visualized Reservoir Characterization While Drilling Technology Improves Understanding of Complex Channel Sand, Assists EOR in a Mature Oilfield in Bo Hai Bay

Abstract

PLxx oilfield is a mature oilfield which has been developed by horizontal wells for several years with water-injection production style. It features with shallow, complex, high challenging unconsolidated channel sand with lateral property variation due to pinch out, stacking or lamination. The thickness of pay zone changes from couple of to ten more meters which brings much high challenge to reservoir delineation while drilling and horizontal well placement execution. The oilfield locates at a faulted belt of Bo Hai Bay among which some small faults may happen. But it's difficult to be identified because of the low S/N ratio incurs from the shallow gas effect on the seismic data. Moreover, uneven flowing zone units exist within sandstone package due to dynamic reservoir production, uncertainty of lateral sand connections and possible inter-well interventions. As such, this makes the oil-water distribution more complicated and the oil-water contact isn't uniform in the sand package. In order to furtherly understand the complex channel sand, place the wellbore in the favorable sweet spot and enhance the oil recovery, a newly-developed visualized reservoir characterization while drilling integrated technology associated with RSS(rotary steerable system), HSVP(high speed data transmission system), RTC(remote transmission connection through Internet) and OSC(operation support center) was employed to optimize the operation efficiency during a three-wells drilling campaign in this oilfield. This newly-developed reservoir characterization technique is the industry innovative fully 9 components measuring azimuthal Electro-Magnetic propagation tool in one single sub. It provides not only the conventional propagation resistivity but also the geo-signal responses in a very quick, flexible way. In one of the case, the unique "Dual-diagonal orthogonal T-R antenna design" ensures the DOI (depth of investigation) as deep as 6.8meters. The reservoir boundaries such as the top, the bottom or the oil-water contact were distinctly characterized and the horizontal drainage section was precisely navigated within the profitable pay zone. The post-well reservoir characterization result is comparable with the seismic profile and very helpful to understand the dynamic reservoir flowing zone unit. The excellent performance is also reflected in the oil production; the initial oil production was increased from 40 m3/day to 69m3/day which is 75% higher than expected. Minimum 25% of oil recovery will be enhanced as forecast.