Introduction

This paper will discuss the development strategy of Japex Oman’s Daleel oil field since its first days until today. Japex Oman entered into an agreement with the government of Oman for the exploration, drilling, and production of crude oil in the sultanate of Oman in 1981. Under this agreement, Japex Oman was awarded a concession area in the northern part of the country, approximately 450 km north-west of the capital area, Muscat. This agreement is based on the production sharing concept.

Exploration & Development

Japex Oman has conducted exploratory work in their concession area for eight years from 1981 through 1989, of which six years are the original exploration term defined in the petroleum agreement and the later two years are the additional exploration term extended by the government and Japex.

The exploratory work composed mainly of seismic work and drilling. The seismic data acquisition and processing of total of 2,883 km covering the whole contract area were done in the initial stage of exploration in order to identify and select leads and prospects.

After the geological compilation and the seismic interpretation, the first drilling campaign started in 1983 comprising of the drilling of six wells. As a result Middle Cretaceous Natih and Lower Cretaceous Shuaiba reservoirs were found at Mezoon structure.

The second drilling campaign started in late 1985, which consists of the drilling six wells. During this drilling campaign, Daleel field was found and the exploratory work was concentrated on the appraisal work for the Daleel discovery, to confirm the real extent and development of the Shuaiba oil reservoir. Since little amount of oil was produced from the Natih formation, the Natih reservoir was excluded from the target horizon to be tested. Concerning the Shuaiba reservoir, rather a uniform oil reservoir of about 24m net thickness was confirmed at Daleel-2, while a thin water bearing reservoir was found at Daleel-3 in the uppermost Shuaiba section.

During additional exploration term four more appraisal wells were drilled around the Daleel pool that proved the field being commercial.

The first phase of development work comprising of the drilling of 20 development wells in the proven area where oil reservoir had been confirmed with the appraisal wells and the seismic evidence. The 20 wells were drilled with 700m well spacing which is considered to be the efficient spacing from the feasibility study. Two of the 20 development wells were plugged and abandoned, Daleel-20 due to lack of reservoir and Daleel-27 due to the reservoir level in the aquifer.

Construction of Facilities and Commencement of Production

　As part of the development phase, an Early Development Facilities (EDF) were rented from and operated by a third party contractor. These facilities were put to achieve early commencement of production and to recover cost quickly. The design capacity of the EDF was approximately 9000 bopd, and consists mainly of a bulk and test separators, heater, storage tanks, and export pumps. At this stage also some permanent facilities were also constructed, such as,

• 3” flowlines from wells to satellite manifolds.
• Three satellite manifolds.
• 3” test & 6” production lines from each satellite manifold.
• Inlet manifold.
• 8” buried trunk line from the EDF to PDO’s 24” line, that is about 14 km away.
• LACT unit at the point of delivery to PDO’s line.

While production continued from the EDF starting from July 1989, the work on the construction of the permanent Gathering Station was going on. When the work on the Gathering Station was completed, the wells were diverted and production started from the Gathering Station in December 1991. The design capacity of the Gathering Station is about 9200 bopd.

Omanisation

Since July 1989, Japex has accelerated its Omanisation, and the percentage of Omani staff has jumped up from 18% at the end of 1989 to approximately 63% at present. Japex has selected the applicants thoughtfully and appointed only qualified and forward looking candidates. Some of them had previous experience, but basically they were all deemed to require further training. To train the newly recruited personnel has been the focal point of Japex since the start, and for that purpose, an efficient and productive “On The Job Training” program has been adopted. Moreover, and in order to acquire the latest knowledge and skills, Japex staff have been and will be sent for short courses abroad.

Conclusion

Due to the geological uncertainty of the Daleel oil field, a stepwise development scheme was adopted by Japex Oman for the proven oil area to the surrounding probable oil areas. In this regard, and as a conclusion, the following points are worth mentioning :

• Continuous drilling of development wells with one rig ,to allow the optimum order of the development well drilling, the drilling operation is done with one rig.

• Application of efficient well stimulation, Emulsified Matrix Acidizing (EMA) was applied to the first 4 development wells and its efficiency of productivity enhancement was compared with that of the conventional hydraulic fracturing in order to determine the most efficient well stimulation method for the development wells.

• Permanent facilities ,the existence of the permanent facilities allowed for the second development phases A & B in addition to the Japex Aswad project to be carried out, with only minor construction work on the flowlines.

• Facilities design for future expansion ,the constructed permanent facilities are designed to allow for the increase in production capacity by the installation of additional facilities.

• Utilization of associated gas as fuel for power generators, heater, and blanketing purposes. However, several studies have been conducted to utilize the gas by gas injection, and the studies in this field are continued.