Optimum Flow Calculation of SBZ Gas Field from IPR Curve using ECLIPSE

Shabazpur Gas Field at a Glance

Shahbazpur Gas Field was discovered by BAPEX (Bangladesh Petroleum Exploration and Production Company Ltd) in 1995 at Bhola, Bangladesh. The production was commenced in 11th May, 2009. In the earlier stage of production, the plant was based on LTX units till late 2014. In 2015, the plant was changed to TEG Dehydration unit base from LTX unit base due to the high condensate and water production rate. Till now, it has the highest production rate compared to the other gas fields owned by BAPEX.

Reservoir Condition

The Shahbazpur structure is a subsurface anticlinal structure situated in the middle of the Bhola Island in the northern margin of Hatia trough of Bengal Foredeep. The Hatia trough is bounded by the Chandpur-Barisal high in the northwest, and by the Chittagong-Tripura Fold Belt in the southeast. The alignment of the NW-SE trending oval shaped Shahbazpur structure is parallel to the Kutubdia structure which is located in Bay of Bengal to the south. Shahbazpur structure is surrounded by Muladi Structure to the Northwest and Kutubdia Structure to the Southeast. The structure started growing probably during Late Miocene and its acme of development took place during Mio-Pliocene sedimentation and ended in Pleisto-Pliocene time. This structure is relatively 69.4 m higher than the Kutubdia structure. The amplitude of the structure increases with depth. There is no surface expression of the Shahbazpur structure and the surface is floored with recent alluvial plain.

Reservoir Depth : 3480 m
Reservoir Pressure: 5400 psi
Reservoir Temperature: 195 F

Gas Composition

The sample was tested at 94 degF temperature and 540 psi pressure in BAPEX laboratory. The determined gas composition is taken as input for plotting phase diagram of the sample in ECLIPSE software. The generated phase diagram in figure-2 shows that cricondenbar (67 bar) is greater than critical pressure (58 bar). It clearly shows that the gas of SBZ gas filed is a dry gas reservoir.

Process Flow Diagram and Process Units

A simple process flow diagram of SBZ gas field is illustrated below.

Pipe Schedules and Valve Rating

There are 5 types of scheduled pipes (XXS, 160, 120, 80 and 40) and 4 types of rated valves (#2500, #1500, #600 and #150) used in the SBZ gas field.

Daily Flow Calculation through Orifice Meter

The daily gas flow through the orifice is measured using the following formula. For better understanding, please read the article 6.7.10 (Flow Measurement) from the book 'Standard Handbook of Petroleum and Natural Gas Engineering' by William C. Lyons and Gary J. Plisga.

Rate of Flow, Qh = C`√(hwPf) in MMSCF/d where C` = Fb * Fpb *Ftb * Fg * Ftf * Fr * Y * Fpr * Fm

Determining Optimum Gas Flow

For well no-2, the officials of SBZ gas field have manually found that considering all factors and variables the optimum flow rate is approximately 14 MMscf/d. But here, we have done an experimental simulation of optimum flow rate using ECIPLSE software and it came out 14.1 MMscf/d for THP of 400 psi which is close to the field result.

Steps Followed in ECLIPSE Software to Determine the Optimum Flow
(Download Generated VFP Table)