M 4 thanh tan the enhancement of seismic prospecting effectiveness for oil and g

Geofizyka Stosowana ZESZYT 6 ZESZYTY NAUKOWE Nr 1323 AKADEMI! GORNICZO-HUTNICZEJ IM. STANISLAWA STASZICA GEOFIZYKA STOSOWANA ZESZYT 6 MAI THANH TAN Zwiekszenie efektywnoéci badart sejsmicznych w poszukiwaniach zló¿ ropy Ì gazu w warunkach basenów osadowych szelfu kontynentalnego w Wietnamie KRAKÓW 1990 LA 4oÌ No. 1323 SCIENTIFIC BULLETINS Ị OF STANISLAW STASZIC ACADEMY | OF MINING AND METALLURGY APPLIED GEOPHYSICS BULLETIN 6 MAI THANH TAN The Enhancement of Seismic Prospecting Effectiveness for Oil and Gas under the Conditions of the Sedimentary Basins in the Continental Shelf of Vietnam CRACOW 1990 NACZELNY REDAKTOR NAUKOWY SCIENTIFIC EDITOR-IN-CHIEF Zdzislaw Kleczek ' NAUKOWY REDAKTOR DZLALU ¬. SCIENTIFIC EDITOR Zbigniew Kasina OF APPLIED GEOPHYSICS RECENZENT oe : CONSULTEE Zbigniew Kasina Adres Redakeji Address Wydawnictwo AGH al.

Szarowaka PL ISSN 0860-7109 Matryos wykonano 2 golowych oryginaliay AKADEMIA GORNICZO-HUTNICZA IM. STASZICA W KRAKOWE Wydanie 1.— Zarréndenia ra 229/00 Ask. druk 9 Oddeno do đướui 1000-06-18 Druk ukoriczone w may 1900 Wytonano w Zakiadzie Graficanym AGH. Kahéw, ul, Kemvory 40 Cantents SUMMALTY Loc cee eee ene ccm e ce see ne ear e eee e nee neees Se rrr Foreword.

Characteristics af the seismogeological models of the sedinen- tary basins in the continental shelf af Vietnam. Sedimentary basins of Vietnam in the Southeast Asia tecto- MAG 8VyS†BN. c Q KH SH on n HS n non n1 Sim son 1 1ó KÝ 1Ý, eee 1. Features of geological structure of sedimentary hasina in the continental shelf of Vietnam.

The characteristics of velocity sectiong. The velncity of certain rock types ín the sedimøn- tary basins of Vietnam. The character of velocity diffarentation of the me4 dium. The chsracteristics df geophysical fields.

The seismiC wave f†i8ìd. The magnetic field. acca eee e een enee ev enee 1. The gravity “leld.

an aassnessedhlee emer ee cecense Analysis of the seismic prospecting effectiveness in the sedi- mentary baains of Vietmam. cece cen eee ener ener weeenaee 2. Seismic prospecting for ail and gas. The process of seismic prospecting for oil and gas in the continental shelf of Vietnam ,.

Evaluating of the effect of seismic prospecting in the se- dimentary basins af Vietnam. The effect af the seismic field methods. The ef?ffect qf seismic data proOCBSS1nQ. The optimal seismic field methods and data proces- sing.

— The study of the relationsnip between tne layered sedimentary media and the seismic prospecting in Vietnam. The characteristics of thin-layered medium. The study of energy absarption characteristics of the laye- red sedimentary hasinsa in Vietnam. esc eee reece eens i "1 13 1P 18 20 21 26 28 28 32 32 40 42 aa +49 31 60 60 65 3.

Solving the theoretical dynamic problem for studying the relationsnip between useful signal ano roises in the condi- thongs cf Vistnam 2. ecw eet e eect aeeenae \,4, The influence of a layered medium on the effect of the de- tarmination af the velocity fiela. emcee tee ena 3. The intluence of a layered medium on the nyperbolic property cf time-distance curves.

The influence of a layered medium on the effect of studying velocity models. Exploitation of the geological information for the atudy of the sedimentary baains of Vietnam according ta seismic dats. Classification of the seismogeological sections in the se- dimentary oasins of Vietnam. Classification of seismogeological complexes.

Classification of seismageological sections. Geological structure of the sedimentary hasins of Vietnam on tne basis of seismic data. ecw ences ese neces nenne 4. Bacbo Gulf basin.

See ve reece ¬" ¬" 4. eee ee ee came n ones eee 4. South Conson baain. or euee "ốc 4.

Central Vietnam basin. abe e eens ec ene s assed 4. Study of seismic stratigraphy of the continental ahelf of Vietnam. Cee ỈỊ gen 1m 6S 1ˆ, ¬".

Seismic stratigraphy in the seismic facies analysis 4. Sedimentary evolution and claasification of seismic facies zones in the continental shelf of Vietnam on the basis of the study of seismic stratigraphy. Application of seismic stratigraphy for discovery of 011 and ges traps’. Evaluating the prospect for o11 and gas in the sedimentar baains of Vietnam 2.

ccc ccc ccc ce tween cen ee cn ents. cà ÒÒÔỒ ¬—-= Streszczanie: Zwigkszania afektywnoáci badsi se)anicznych w poszu- kiwaniach 2262 ropy i gazu w warunkech basendw oeadowych szelfu kon tynentalnego w Wietnamie. 7P 79 79 8á 32 93 94 98 98 "102 10? + 110 111 112 119 125 129 132 1313 142 Mai Thanh Tan THE ENHANCEMENT OF SEISMIC PROSPECTING EFFECTIVENESS FOR OIL AND GAS UNDER THE CONDITIONS OF THE SEDIMENTARY BASINS IN THE CONTINENTAL SHELF OF VIETNAM Summary. Under the complicated geclogical conditions of the sedi- mentary basins of Vietnam, it is necessary to enhance the effect of the seismic prospecting for oi] and gas.

In order to solve this problem, a series af studies has been conducted by the author.the present work, the author has described the complicated charac- teristics of the seismogeological model of the medium. The velocity dif- ferentation and thin-layered structure of the medium have been made cle- ar. Besides the velocity, the energy absorption coefficient of the medium has been determined for the first time in Vietnam. These problems are in tight relation with the possibility of the application of the seismic ethod.

According to the author, the sedimentary sections in the continental shelf of Vietnam have been divided into 5 velocity complexes, 4 seismo- geological complexes and 5 kinds of seismogeological sections. These di- visions are very necessary for the geologicai-geophysical studies. By solving the theoretical dynamic problems, the attenuation of the reflected wave energy, the signal-to-noise ratio have been determined quantitatively. By means of the digital modeling method, the influence of the complicated medium on the effect.of the seiamic data processing (C.

stacking, velacity model construction etc.) has been determined. With the aim to clarify the nature of the medium and to prospect di- rectly for oil and gas, the seismic-stratigraphy methods especially the @ethod of recognition of seismic facies, have been applied for the first time in Vietnam. On the basis of the studies, the sedimentary evolution, the expression of seismic facies, the identification of seismic comple- xes, the existence af oil and gas traps etc., have been studied. | The results studied by the author contribute to the enhancement of seismic prospecting for oi] and gas in Vietnam, and permit to conclude that in the complicated geological conditions of Vietnam there is a great potential prospect for oi] and gas and that the enhancement of the seismic method always playa a very important role.

The seismic method can be used not anly to study geological structure but also to prospect directly for oil and ges. FOREWORD In Vietnam, seismic prospecting for oil and gas has been carried out on shore for 25 years and is now heing developed in the large continental shelf. With the continuous renewal of methodology and equipment, the infor- mation obtained is more and more complete creating the wonderful develop- ment af seismic methods. The obtained results greatly contribute to the clarification of the geological structure of this region and the prospec- ting for oil and gas.

At the same time, they show that the sedimentary basins of Vietnam are of complicated characteristics. In the past, sei- smic methods were chiefly applied to studying the medium morphology. Now, there is a basis for a thorough study of the information on wave fieids, for seeing through the very nature of the media themselves and for solving problems regarding seismic stratigraphy, seismic lithography and direct Prospecting for oil and gas. In recent years, seismologists in Vietnam have concentrated their efforts aon the improvement of technique and equipment (changing the wave generation and receptive conditions, using powerful interferential systems, digital recording technique, etc.) and, at the same time, have done their best to enhance the effectiveness of seismic data processing.

Stress should be laid on the fact that these studies have ushered the seismic method into powerful developments though still limited. For the enhancement of the effectiveness of seismic praspecting in Vietnam, the author of this work has conducted a series of studies in different directians: - study of the chracteristics of the seismogeological model of the se- dimentary basins in the continental shelf af Vietnam an the determination of their relations with the requirements of seismic prospecting, in which the author tried to clarify the difference of seismic velocity in the layered sedimentary basins, the characteristics and distribution of sei- smageclogical sections; 10 - study of the conditions of the wave generation and observation syster for increasing the signal-to-noise ratio, ~ conducted experimental and theoretical studies in the nature of the wave field and the signal-to-noise relatian in the complicated media, - study of the effect cf processing and interpretation providing that the sedimentary basins of Vietnam are layered in a complicated way, - study of the seismic stratigraphy methods to prospect for cil and gas traps in non-structural formations in Vietnam. The present wark has been written in the form of a monograph basing ci results obtained by the author in connection with the problems of enhan- cing the effectiveness af seismic prospecting in Vietnam, including some author s earlier works (Mai Thanh Tan 1975,1982b, Mai Thanh Tan and Doung Hung Hai 1987), Mai Thanh Tan et al. The present study entitled "The enhancement af seismic prospecting effectiveness for oil and gas under the conditions of the sedimentary ba- sins in the cantinental shelf of Vietnam" has been written at the Institu te of Geophysics, the Academy af Mining and Metallurgy, Cracow, Poland.

Taking an opportunity, the author wishes to express his deepest grati- tude to Professor Jerzy Kowalczuk and Docent Zhigniew Kasina for their helpful and constructive discussions as well as for their critical remarks on the manuscript. The author is also grateful tao Professor Stanistaw Ma- teoszewski, the Director of the Institute of Geophysics AMM, who has pro- vided facilities for carrying out this work. The author s acknowledgement is also extended to Doctors Truong Minh, Pham Nang Vu, Nguyen Giao, Kaja Pietsch, Ryszard Slusarczyk, and other Calleagues for their valuable suggestions. , The author has a pleasure to thank General Departments, Institutes and Colleges in Vietnam such as the Research Institute of Oil and Gas, the General Department of Oil and Gas, the General Oepartment of Mining and Geology, the Department af Geophysics and the Hanoi Mining and Geology College for the field measurements and drafting of the works.

Finally, the author feels greatly indebted to the Staff of the Insti- tute af Geophysics, Faculty of Prospecting Gealogy and the Academy of Mining and Metallurgy, Cracow Poland, for fecilities and favourable condi- tions to acgomplish this scientific work. CHARACTERISTICS OF THE SEISMOGEOLOGICAL MODELS OF THE SEDIMENTARY BASINS IN THE CONTINENTAL SHELF OF VIETNAM The characteristics of the seismogeaclogical models of the medium are in tight relation with the process of the application af seismic methods and have a great influence on it. The sedimentary basins of Vietnam, being in relation with gas and oil perspective, are large and have a complex geological structure, therefore in spite of many researches into this problem, there have still been many restrictions uftil now. In this chapter, the author has exploited the geological and geaphysi- cal information with the aim to make clear the geological structure, phy- Sical nature and geophysical fields of the medium of the sedimentary ba- Sins af Vietnam.

These questions are in tight relation with the possibli- ty of ameliorating the effect of the seismic method in the oil and gas Prospecting service in Vietnam.