Abstract

PETRONAS is developing a marginal gas field (K Field) in Indonesia. The target reservoir is classified as unconsolidated in nature based on geological studies and core samples obtained from the field. The planned wells in the field comprises of long inclined well with requirement of downhole sand control. Gravel packing in long inclined well is operationally difficult and costly, rendering development of this marginal gas field uneconomical.

Alternatively, Open Hole Stand Alone Sand Screen (OHSAS) completion was proposed and is supported by the sieve analysis. However, sand screen in gas well is susceptible to erosion due to expected high gas flow velocity in annular section. An innovative sand control completion was proposed with the main objective to segmentize the flow into multiple compartments in order to reduce annular flow velocity, which will potentially lead to reduced erosion on sand screen. This concept has been successfully piloted in a horizontal gas well with maximum production of ~20MMscfd.

In order to apply the concept in an inclined well, CFD modelling is conducted to assess the gas velocity distribution of the concept in a long inclined open hole as it is expected that there will be variations in the pressure and inflow distributions between horizontal and inclined wells. The pressure and velocity profiles obtained from CFD in base pipe and annular section for vertical well is compared to those of inclined wells (14, 45, 76 degrees). Results from CFD modelling indicates that the effects of well inclination has a negligible effect on base pipe and annular velocity distribution for different segmentizer placement distance.

Apart from CFD analysis, parametric sensitivity study on flow rate and sand loading were conducted using an in-house proprietary methodology to optimize the number of segmentizer along the six development wells. Study indicates that flow segmentizers are capable to reduce the annular velocity below the critical limit for erosion for the 6 proposed development wells which results in reduced potential erosion risks on the sand screen. Subsequently, based on the recommendation from the study, OHSAS completion with flow segmentizers was successfully installed in 6 wells in K field in 2014. This has provided strong indication that OHSAS with flow segmentizers is a technically viable well completion option which has significant economic benefit for potential application in developing marginal gas field. K Field has achieved first gas on September 2015 with 6 wells currently online with sand production limit of below 0.5 lb/MMscf.

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