New 7-in. Dual-Trip Multi-Zone Gravel Pack System Provide Cost Efficient Completions for Offshore China Development
Authors: Wah Kee Yong , Ming Deng Jian , Jones Ralph H. , Larimore David R. , Yap Weekam 
Published: December 2007

Traditional completion scenarios requiring sand control in multiple zones often require a minimum of 6 to 7 days for gravel packing operations, depending on the length of each zone and the time needed for installation of the completion equipment. If the gravel-packing operations are to be performed in zones with varying reservoir conditions and lengths, the operations can take even longer.

This paper concerns development of a 10-well area of the QK field, located offshore in Bohai Bay in the Peoples Republic of China operated by China Offshore Oil Bohai Corporation (COOBC). The field development required a completion scenario that would be consistent with the current low oil prices that prevailed at the time the project was initiated. Therefore, the operator was presented not only with the challenge of designing a completion consistent with the constrained economic climate but also one that would address the difficulties inherent to friable unconsolidated formations with different length zones and heavy hydrocarbon production.

Reviews of available options were performed, and the operator and service/equipment supplier agreed that a 7-in. system that would have the flexibility to isolate zones of different lengths without requiring multiple trips, and thus, would meet the needs to complete the wells. Unfortunately, no currently available systems had the necessary capabilities. Therefore, a project was initiated to develop a system. The project resulted in design of the first 7-in., dual-trip, multi-zone (DMTZ) gravel-pack system worldwide.

This paper will discuss how COOBC along with service suppliers were able to design and complete 10 wells in the QK field development in a timely and cost effective manner. Fig. 1 is a map showing the location of the QK field.

Introduction

The QK field is located Bohai Bay, which is east of Beijing near the Sourtn shore. The QK field is comprised of multi-layered river-sand formations with close proximity of water aquifers near the oil reservoirs.

The production intervals are characterized by unconsolidated, friable, high permeability sandstones formations. The hydrocarbon production has a low API gravity and contains high wax content. To achieve economical production goals multiple intervals must be commingled. Electric submersible pumps (ESPs) and water-injection are used to enhance production.

The design critia was very similar to the South China Sea Xijang field development presented in SPE paper 299561 and SPE paper 36950.2 Although total field development was planned for 26 wells, this discussion concerns the 10 wells completed with the new 7-in. DTMZ gravel-pack system.3

Several conditions had to be satisfied:All QK completions would require internal multi-zone gravel packs because of the friable unconsolidated formation.Wells in the QK field would be produced at high flow rates with escalating water cuts.Because of the constrained climate in the oilfield at the time completion was needed, capital expenditure for the venture was limited.

Using the above as the primary requirements, the design team was commissioned to develop the completion plan.

Reservoir Information

The QK field development contains fourteen river-sand formations with separate oil-water contacts. The fields are comprised of multiple-layered reservoirs that must be commingled for economical production. Productive interval depths range from 1600 m to 2100 m. (5249-ft to 6889-ft) true vertical depths (TVD) with 14 river sand zones. Maximum reservoir temperatures vary from 67° to 74°C.