Mohammed M. Amro

Investigation of Polymer Adsorption on Rock Surface of Highly Saline Reservoirs

Blocking or reducing water production from oil wells is a serious problem in oil industry. Two types of polymers, namely, polyacrylamide (PAA) and polysaccharides (xanthan) have been investigated in this paper. The viscosity of both polymer solutions was first evaluated at different salinities, shear rates and concentrations. Afterwards, the solutions were injected into core samples to examine the adsorption on the rock surface by calculating the resistance factor as well as the residual resistance factor. Also, the effect of the injection rate of the polymer solutions has been studied. The results show that xanthan solution is tolerant of high salinity (20 %), while PAA solution is very sensitive to salt. Both polymer solutions show a pseudoplastic flow as a function of the shear rate. The core sample experiments show that both polymer solutions suffer a reduction in the adsorption rate with salinity increase. However, xanthan shows acceptable values even with a salinity up to 20 % and a temperature of 60 °C. Therefore, xanthan can be recommended to shut off water in high salinity and high temperature reservoirs. It was also found that the lower the injection rate the higher the adsorption on the rock surface.

Influence Factors of Fracability in Nonmarine Shale

Fracability, the capability of shale that can be fractured effectively, is the most critical evaluation parameters in shale gas production. At present, it is generally recognized that using mineral composition and rock mechanics parameters to represent shale fracability is difficult to fully reflect the comprehensive properties of shale in hydraulic fracturing. However, so far all fracturing research about shale gas is almost considering marine shale and the understanding of shale fracability is confined and trapped within marine shale. Since shallow deposit of sedimentary strata in China is non-marine (lacustrine) facies sediments, China pay increasing attention to non-marine shale, which is opposite to the situation in Europe, and with the deepening of shale gas exploration, Europe will focus more on the non-marine shale in following decades. Due to the fact that lacustrine shale deposits differ from marine deposits in sedimentary environment, the former are always with frequent sand and mud interbed, interlayers development. Therefore, the influence factors of fracability in non-marine shale seemed more complexes and the research of shale fracability becomes more significant. After general contrastive study of sedimentary environment, gas generation, mineralogy and physical properties of non-marine and marine shale based on literature data, this paper separately analysed the fracability influence factors (including sedimentary environment, mineral composition, diagenesis, brittleness, nature fracture, etc.) of non-marine shale focused on the Mesozoic Triassic Yanchang Formation shale in Ordos Basin of China. Moreover, comprehensive consideration of all above influence factors and statement of some fracability evaluation methods have been implemented. Unified and quantitative evaluation of fracability influence factors in non-marine and marine shale has been discussed afterwards. The summary of main influence factors of fracability in non-marine shale not only improved the shale fracability research, but also could guide the hydraulic fracturing practice.

Investigation on crude oil penetration depth into soils

The main objectives of this paper are to study crude oil migration as a toxic fluid, its rate of penetration, and its consequences for eventual treatment. To achieve these objectives, an experimental model was designed comprising two separated columns, filled with soil and other rock types to simulate a real case scenario. Crude oil penetration depth versus time was recorded by taking soil samples whereas water samples were collected from the wet system to analyze the penetrating liquid. The results show that penetration depth was greater in the wet system during the early stages rather than in the dry system. However, with time, penetration becomes more developed in both systems. Overall penetration in the final stage was found to be significantly higher in the dry system. In addition, it was observed that during crude oil migration in dry system, chromatographic separation of crude oil components has occurred obviously. The obtained results reveal that immediate treatment must be performed in both systems but particularly in the wet system, due to its higher initial penetration rate.

A new practical approach to evaluate near wellbore formation damage parameter based on well test analysis for gas reservoir

Prediction of degree of near-wellbore damaged caused during drilling and completion is extremely difficult and challenging in any reservoir development program. It plays a vital role on decision making, specifically when the decision has to be made based on inflow performance relationship (IPR) analysis. Skin factor used for most of the IPR models are either calculated from analytical models depending on the near wellbore conditions (e.g. open hole, perforated, gravel packing etc.); or predicted based on expensive well test data. While accuracy of the predicted results depends on the accuracy of input parameters available to feed into model, nevertheless this approach can generate range of uncertainties with misleading predicted results that significant effect on decision making. This paper presents a simplified practical method of estimating the extent of damage and amount of skin in a reservoir. Correlations for the permeability in the damage zone have been developed as a function of the average reservoir permeability in the drainage area of reservoirs for steady, stabilized or transient flow conditions. The model uses well deliverability test data to predict average permeability in the drainage zone. The model has been applied to different cases using representative field test data for high and low permeable reservoirs. It has been demonstrated that the proposed model exhibits very good approximation of damage components affecting reservoirs. From this analysis, it could also be concluded that by using data from unsteady flow deliverability tests, it is possible to get a good estimation of the damage skin in a reservoir and its extent. This is valid as long as the damage does not exceed the transient drainage radius. Exceeding the transient drainage radius will imply deriving very large skin values from the test, and this is rare in most cases.