Study on the Asphaltene Deposition Prediction Theory and Method in Deepwater Crude Oil Pipelines

Lu, Ping (CNOOC China Limited) | Du, Xiaying (CNOOC China Limited) | Yang, Li (Southwest Petroleum University) | Qu, Zhaoguang (CNOOC China Limited) | Liu, Chunyu (CNOOC China Limited)

OnePetro 

ABSTRACT

Asphaltene deposition is one of the key technical problems in the safe production and transportation of deepwater asphalt base crude oil. This paper analyzes the asphaltene deposition condition and its existence in deepwater crude oil pipeline system by theoretical and experimental study. According to the thermodynamic behavior of crude oil system, the prediction model of its asphaltene deposition conditions is established, and combined with the pressure and temperature drop analysis of deepwater crude oil pipeline system, the prediction method of asphaltene deposition amount and location in deepwater pipelines is preliminarily formed. This study lays a foundation for further study on the flow assurance of deepwater asphalt base crude oil transportation system.

INTRODUCTION

Asphaltene deposition in deepwater pipeline is an important technical problem in the present petroleum industry. Due to the challenging deepwater environments, especially low temperature, adhesion of asphalt base crude oil is strong and liquidity is poor (Sara and Abbas, 2013). Once solid blockage appears in deepwater pipeline, it is very difficult to resume production and remediation cost is extremely high, which presents a high risk to oil production.

According to the special environment of deepwater oil pipeline, the asphaltene deposition condition and its existence in the deepwater oil pipeline system are analyzed based on the changes of pressure and composition of crude oil system. Taking K96 crude oil, KD32 emulsified oil and dewatered oil as the research objects, the rheological properties and corresponding microscopic shapes of the oil samples before and after adding n-heptane are tested and analyzed by using rheology and image analysis technology. Meanwhile, the mathematical model of asphaltene deposition in deepwater crude oil pipeline is established to predict the asphaltene deposition condition, and the prediction method of the asphaltene deposition amount and location in deepwater oil pipeline is initially formed. This is not only necessary but also very challenging to the flow assurance of deepwater asphalt base crude oil transportation system.