The highly reactive FIQA shale used to compel well engineers in The Sultanate of Oman to plan the drilling phase of surface and intermediate sections based on time exposure to aqueous drilling fluid system (WBM). The new approach of drilling the timedependent FIQA shale formation using Casing-while-Drilling (CwD) allows well engineers to plan prospect top/intermediate wellbore sections differently by enhancing the drilling performance and reducing the risk of setting casing strings shallower, external corrosion due to aquifers, and getting stuck or reaming continuosly while drilling conventionally. The technical feasibility study, planning, risk assessment, execution, as well as the lessons learned during the process of drilling top sections are described in this document. The CwD team compares the drilling performance of several offset wells and suggest actions to improve the CwD technology in Oman.Two surface sections were drilled successfully with large OD casing strings. Both surface sections 17½" and 22" reached 750m and 894m measured depth, respectively, reducing drilling phase by 40-45% in comparison with the average in the field. The exposure time of FIQA to aqueous environment was reduced considerably eliminating conditioning trips and non-productive-time (NPT) associated with wellbore instability. The volume of returns as cementing increased from 20% -with conventional drillstring -to 92-98% of pumped excess volume. CwD will allow drilling teams to slim down top holes by drilling/casing much deeper sections within less time preventing FIQA from collapsing and avoiding potential applications of Oil Based Mud (OBM). This new technology may also allow the optimization of existing rigs reducing cost and size of rig prints, as well as minimize HSE risk while handling large-OD casing and extremely heavy DC's.Simulation of the drilling phase using torque/drag and BHA-analysis software were run. The drillable PDC bit performance is compared to bit-records from offset wells recently drilled with conventional BHA's. The effect of CwD on resulting uniform cement sheath (related to the "smear effect") and the reduced size of cuttings at surface which positively aid on preventing flowline plugging as an unplanned event will be described.It is important to highlight that Nonretrievable 17½"x13⅜" and 22"x18⅝" CwD with drillable bit and the casing drive mechanism, did not require any rig modification. The optimization of the process as well as the familiarization of drilling teams with the main components of the CwD system, will lead to a long, demanding scope for its implementation in several fields in Oman.

In the last decade, hydrocarbon production from low-permeability reservoirs has been on the rise. Multi-stage hydraulic fracturing is the most common technology used to make production from such reservoirs economically viable. Radioactive-tracers and production logging, which are usually used to assess fracture flow efficiency, do not always provide reliable information in terms of the fracture effectiveness and total frac flow height. An advanced technique described in this paper not only can identify active fractured intervals but also quantify the inflow profile. A novel technique was developed to locate fracture inflows and quantify inflow profiles in hydraulically fractured wells. It builds on the industry-proven combination of Spectral Noise Logging and High Precision Temperature Logging. This technology was initially implemented for qualitative and quantitative analysis of reservoir flows, including those through leak points, cement, reservoir rock matrix and reservoir fractures. Fracture flow intervals are located using a new-generation of Spectral Noise Logging tool with wider dynamic and frequency ranges. Quantitative inflow profiles are derived by temperature modelling. The technology described in this paper allowed assessment of hydraulic fracturing effectiveness in the producing wells of Petroleum Development Oman. Three case studies are presented to demonstrate the application of this technology in two producing gas-condensate wells and one oil well, one vertical gas producer and the other horizontal, drilled into clastic low-permeability heterogeneous layer-cake reservoirs and therefore requiring multistage hydrofracturing for commercial hydrocarbon production. Production profiles were determined for all wells, with inflow splits between producing zones quantitatively analysed using temperature modelling, matching the recorded and modelled temperatures, pressures and phase compositions, and taking into account surface data, such as production history and separator test data, and PVT fluid properties. Spectral Noise Logging was used to determine the frac flow intervals. In the vertical well, the survey was conducted at three different flow rates to improve inflow quantification by matching three data sets. The survey results were used to successfully evaluate the effectiveness of multi-stage hydraulic fracturing and fracture height. The acquired information was used to improve hydraulic fracturing planning and design for the field. One of the advantages of applying this technique for fracture flow evaluation is its ability to survey wells under existing operating conditions without shut-in and production deferment. As opposed to conventional production log with spinner, described technique can locate and quantify flow behind pipe.