Core Flood Investigation Into Asphaltene Deposition Tendencies in the Marrat Reservoir, South East Kuwait

Abstract

Asphaltene precipitation can have profound effects on oil production during miscible flooding, heavy oil recovery, or even primary depletion. Even though asphaltene precipitation and eventual deposition have been known to have strong effects on permeability reduction (Turta et al., 1997;Minssieux et al., 1998), quantitative analysis of the process has not been studied extensively. This paper describes experimental work conducted to study the precipitation and deposition tendencies of asphaltenes within the rock material in the Marrat reservoir, South East Kuwait. Live asphaltenic reservoir fluids and carbonate cores of the Marrat reservoir were recovered and used at reservoir pressure and temperature conditions during core flood experiments. The live Marrat reservoir fluid was fully characterized, and subjected to pressure depletion tests to determine the asphaltene onset point at various temperatures.The results reveal preferential deposition of the precipitated asphaltenes with respect to the rock material. The characterization of the rock materials by CT-Scans had indicated the presence of local occluded porosities. These occluded sites were found to be the main influence on the pattern of deposition seen in the core samples. The study shows clearly that although asphaltenes may precipitate and deposit from the Marrat reservoir fluid, the propensity for permeability damage is in fact determined by the nature of the rock material. In addition, the tendency of the precipitated asphaltenes to aggregate into larger flocs that are generally friable influences the rock damage potential.Handling and treatment of asphaltenic fluids will continue to impact on reservoir operations, project costs and recovery efficiencies. Understanding the nature of asphaltenes and how they impact on the sub-surface behaviour of reservoir fluids will become more pertinent, as global oil demand forces a move towards heavy oils and / or highly asphlatenic fluids.

Asphaltene Deposition Preference and Permeability Reduction Mechanisms in Oil Reservoirs: Evidence from Combining X-ray Microtomography with Fluorescence Microscopy

“…In the experiments of Takahashi et al, a larger amount of asphaltene was left behind in the more heterogeneous carbonate core than in the more homogeneous sandstone core although no significant permeability reduction was observed. Rahmani et al also found that the asphaltene deposits were confined to sites of occluded pores, which did not result in severe damage to the reservoir.…”

“…In the experiments of Takahashi et al, 98 a larger amount of asphaltene was left behind in the more heterogeneous carbonate core than in the more homogeneous sandstone core although no significant permeability reduction was observed. Rahmani et al 99 also found that the asphaltene deposits were confined to sites of occluded pores, which did not result in severe damage to the reservoir. The coupling effect of the gradual adsorption and pore blockage consequently predicts a better reservoir conductivity than single-factor models, which, on the other hand, means that the early stage of asphaltene deposition is more inconspicuous than previous predictions have suggested.…”

A New Experimental Approach for Hydraulic Fracturing Fluid Damage of Ultradeep Tight Gas Formation

“…For tight or shale cores, it is usually infeasible to identify which is the primary damage factor by the traditional steadystate measurement core flooding apparatus due to long measurement time (hours or even days) and the gauge accuracy (pressure gauge and flowmeter) [15]. According to experimental theory, permeability measurements in the laboratory can be divided into two categories: the steady-state method and unsteady-state method [16].…”

“…The formation water flows continuously on the surface of the rock sample with flow pressure P m and back pressure P b . Continuously monitor the change of the downstream pressure Pð L, tÞ until it reaches the upstream flow pressure P m P m , P 0 , PðL, tÞ, and equations (4) and (5) were used to obtain the liquid permeability K ini2 of the rock sample Close valves (8)-(17) and open special core gripper (7), intermediate vessel(6), gas pressure regulating valve(22), nitrogen gas bottle (3), and valves(15) and(16). Adjust gas pressure regulating valve(22), setup the pressure, and push the working fluid into the surface of the rock sample for approximately 5 hours (7) Close valves (8)-(17) and repeat procedures (2)-(5).The measured liquid permeability of the damaged rock sample is K CSM (8) The damage rate of working fluid to the core D CSM was calculated through equation…”