CONSTRUCTION OF A THREE-DIMENSIONAL GEOLOGICAL AND GEOPHYSICAL MODEL OF THE ALAN FIELD

ABSTRACT

This article discusses the construction of a three-dimensional geological and geophysical model of the Alan gas condensate field, including the process of building a digital three-dimensional geological model. And also in this article, a lithological model of the Alan gas condensate field is considered, which turns off the rescaling of the logging results and a lithological model in the context of the Alan gas condensate field.

АННОТАЦИЯ

В статье рассмотрены вопросы построения трехмерной геолого-геофизической модели газоконденсатного месторождения Алан, в том числе процесс построения цифровой трехмерной геологической модели. В данной работе также рассматривается литологическая модель газоконденсатного месторождения, который выключает в себя ремасштабирование результатов ГИС и литологическая модель в разрезе  месторождения.

Keywords: Gas and gas condensate fields (GCF), gas-hydrodynamic studies (GDT), digital three-dimensional geological model, lithological model, GIS, upscaling.

Ключевые слова: Газовые и газоконденсатные месторождения (ГКМ), газогидродинамические исследования (ГДИ), цифровая трехмерная геологическая модель, литологическая модель, ГИС, ремасштабирования.

Currently, gas is produced in Uzbekistan mainly from three oil and gas regions: Ustyurt, Bukhara-Khiva, South-Western Gissar, more than half of the fields in these regions are at the final stage of development [1-3]. The hydrocarbon deposits of Southwestern Uzbekistan are located within the Chardzhou and Bukhara stages, most of them are associated with anticlines [4-5].

The main volume of current gas production in Uzbekistan falls on large long-term developed fields with relatively high residual reserves, which include the Alan GCF [6]. Paleozoic, Jurassic, Cretaceous, Paleogene, Neogene, Quaternary deposits take part in the geological structure of the Alan deposit.

According to lithological features and geophysical characteristics, two types of section discovered by exploratory wells are clearly distinguished in the area of the Alan gas condensate field: reef and non-reef. At present, the construction of digital three-dimensional (3D) geological and hydrodynamic models of hydrocarbon deposits is one of the main requirements for calculating hydrocarbon reserves. In turn, this model is the basis for building a hydrodynamic model necessary for designing the effective development of oil and gas fields. With the help of geological modeling, the structure, structure, as well as the distribution of porosity in space, saturation of reservoir reservoir layers are determined.

The construction of a geological 3D model of the Alan field was carried out using the Schlumberger-Petrel software recommended for building permanent models of oil and gas fields. On fig. 1 shows the process of building a digital three-dimensional geological model, which includes the following steps:

Figure 1. The process of building a digital three-dimensional geological model

The structural model is understood as the construction of stratigraphic surfaces of the corresponding horizons. The lithological model implies the distribution of reservoirs and non-reservoirs in space. The reservoir properties model (RPM) includes the spatial distribution of porosity and permeability. To build a facies-lithological model based on the results of logging interpretation, a discrete NTG curve (reservoir-non-reservoir, (Fig. 2) was obtained.

Figure 2. Upscaling of well logging results

NTG curves were obtained by identifying effective intervals in the section based on porosity curves. The boundary value for porosity was taken to be 5% As a result, in intervals with porosity less than 5%, the discrete NTG curve had a value of 0, and in intervals greater than 5% - 1. Then, the discrete NTG curve was averaged (rescaled) onto a three-dimensional grid. Due to the fact that when modeling this property, the modeled area is divided into cells by creating a 3D grid, each grid cell is assigned a single value for each property. Rescaling was carried out using the Scale Up Well logs module.

Figure 3. Lithological model of the Alan GCF

Figure 4. Lithological model in the section of the Alan GCF

When distributing NTG properties, variogram analysis was carried out for each reservoir separately. Based on the rescaling done, the above distribution was carried out. The construction of a lithological model, shown in Figures 3, 4, is reduced to assigning a code to the cells of the grid, which corresponds to a certain lithological type (reservoir-non-reservoir), into which a given reservoir must be divided.

A characteristic feature of the XV-HP horizon section is the frequent alternation of reservoir and non-reservoir rocks. The open porosity of rocks of the XV-HP horizon was studied on 107 samples. The range of porosity here is from fractions of a percent to 33%. The permeability of reservoir rocks of the XV-HP horizon was studied on 26 samples.

In conclusion, it can be said that, according to lithological features and field geophysical characteristics, two types of section discovered by exploration wells are clearly distinguished in the area of the Alan gas condensate field: reef and reef-free. In the carbonate formation that makes up the productive section of the deposit, the following horizons are distinguished: XVI, XV subreef, XV reef and XV overreef.

References:

1. И.М. Фык, Е.И. Хрипко «Основы разработки и эксплуатации нефтяных и газовых месторождений»: учебник / – Харьков: Фолио, 2015. – 301 с.
2. В.А. Амиян, Н.П. Васильева «Добыча газа». М.: - Недра, 1974. – 312 с.
3. Мирмухамедов С.С., Рустамов Ш.З., Адизов Б.З., Орипова Ш.К. «Актуальность предотвращения самоглушения газовых скважин химическими методами» // “Kimyo va kimyo ta’limi muammolari” Qoʻqon 2022. 68-69 b.
4. Газовые и газоконденсатные месторождения: Справочник / Под ред. И.П. Жабрева, Изд. 2-е, перераб. и доп. М., 1983.
5. Чернов И.В. Геологическая изученность месторождений Юго-Западного Узбекистана // «Территория Нефтегаз», июнь 2016. № 6, С. 40-47
6. Орипова Ш.К., Адизов Б.З. «Химический состав пластовых вод верхнеюрских карбонатных отложений ГКМ Алан» // “Наука и инновации” Международная научная конференция Молодых учёных. Т. 2022. 422-423 c.